





Internet Engineering Task Force (IETF)                        Y.-K. Wang
Request for Comments: 7798                                      Qualcomm
Category: Standards Track                                     Y. Sanchez
ISSN: 2070-1721                                               T. Schierl
                                                          Fraunhofer HHI
                                                               S. Wenger
                                                                   Vidyo
                                                        M. M. Hannuksela
                                                                   Nokia
                                                              March 2016


       RTP Payload Format for High Efficiency Video Coding (HEVC)

Abstract

   This memo describes an RTP payload format for the video coding
   standard ITU-T Recommendation H.265 and ISO/IEC International
   Standard 23008-2, both also known as High Efficiency Video Coding
   (HEVC) and developed by the Joint Collaborative Team on Video Coding
   (JCT-VC).  The RTP payload format allows for packetization of one or
   more Network Abstraction Layer (NAL) units in each RTP packet payload
   as well as fragmentation of a NAL unit into multiple RTP packets.
   Furthermore, it supports transmission of an HEVC bitstream over a
   single stream as well as multiple RTP streams.  When multiple RTP
   streams are used, a single transport or multiple transports may be
   utilized.  The payload format has wide applicability in
   videoconferencing, Internet video streaming, and high-bitrate
   entertainment-quality video, among others.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7798.








Wang, et al.                 Standards Track                    [Page 1]

RFC 7798               RTP Payload Format for HEVC            March 2016


Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................3
      1.1. Overview of the HEVC Codec .................................4
           1.1.1. Coding-Tool Features ................................4
           1.1.2. Systems and Transport Interfaces ....................6
           1.1.3. Parallel Processing Support ........................11
           1.1.4. NAL Unit Header ....................................13
      1.2. Overview of the Payload Format ............................14
   2. Conventions ....................................................15
   3. Definitions and Abbreviations ..................................15
      3.1. Definitions ...............................................15
           3.1.1.  Definitions from the HEVC Specification ...........15
           3.1.2.  Definitions Specific to This Memo .................17
      3.2. Abbreviations .............................................19
   4. RTP Payload Format .............................................20
      4.1. RTP Header Usage ..........................................20
      4.2. Payload Header Usage ......................................22
      4.3. Transmission Modes ........................................23
      4.4. Payload Structures ........................................24
           4.4.1. Single NAL Unit Packets ............................24
           4.4.2. Aggregation Packets (APs) ..........................25
           4.4.3. Fragmentation Units ................................29
           4.4.4. PACI Packets .......................................32
                  4.4.4.1. Reasons for the PACI Rules (Informative) ..34
                  4.4.4.2. PACI Extensions (Informative) .............35
      4.5. Temporal Scalability Control Information ..................36
      4.6. Decoding Order Number .....................................37
   5. Packetization Rules ............................................39
   6. De-packetization Process .......................................40
   7. Payload Format Parameters ......................................42
      7.1. Media Type Registration ...................................42
      7.2. SDP Parameters ............................................64



Wang, et al.                 Standards Track                    [Page 2]

RFC 7798               RTP Payload Format for HEVC            March 2016


           7.2.1. Mapping of Payload Type Parameters to SDP ..........64
           7.2.2. Usage with SDP Offer/Answer Model ..................65
           7.2.3. Usage in Declarative Session Descriptions ..........73
           7.2.4. Considerations for Parameter Sets ..................75
           7.2.5. Dependency Signaling in Multi-Stream Mode ..........75
   8. Use with Feedback Messages .....................................75
      8.1. Picture Loss Indication (PLI) .............................75
      8.2. Slice Loss Indication (SLI) ...............................76
      8.3. Reference Picture Selection Indication (RPSI) .............77
      8.4. Full Intra Request (FIR) ..................................77
   9. Security Considerations ........................................78
   10. Congestion Control ............................................79
   11. IANA Considerations ...........................................80
   12. References ....................................................80
      12.1. Normative References .....................................80
      12.2. Informative References ...................................82
   Acknowledgments ...................................................85
   Authors' Addresses ................................................86


1.  Introduction

   The High Efficiency Video Coding specification, formally published as
   both ITU-T Recommendation H.265 [HEVC] and ISO/IEC International
   Standard 23008-2 [ISO23008-2], was ratified by the ITU-T in April
   2013; reportedly, it provides significant coding efficiency gains
   over H.264 [H.264].

   This memo describes an RTP payload format for HEVC.  It shares its
   basic design with the RTP payload formats of [RFC6184] and [RFC6190].
   With respect to design philosophy, security, congestion control, and
   overall implementation complexity, it has similar properties to those
   earlier payload format specifications.  This is a conscious choice,
   as at least RFC 6184 is widely deployed and generally known in the
   relevant implementer communities.  Mechanisms from RFC 6190 were
   incorporated as HEVC version 1 supports temporal scalability.

   In order to help the overlapping implementer community, frequently
   only the differences between RFCs 6184 and 6190 and the HEVC payload
   format are highlighted in non-normative, explanatory parts of this
   memo.  Basic familiarity with both specifications is assumed for
   those parts.  However, the normative parts of this memo do not
   require study of RFCs 6184 or 6190.








Wang, et al.                 Standards Track                    [Page 3]

RFC 7798               RTP Payload Format for HEVC            March 2016


1.1.  Overview of the HEVC Codec

   H.264 and HEVC share a similar hybrid video codec design.  In this
   memo, we provide a very brief overview of those features of HEVC that
   are, in some form, addressed by the payload format specified herein.
   Implementers have to read, understand, and apply the ITU-T/ISO/IEC
   specifications pertaining to HEVC to arrive at interoperable, well-
   performing implementations.  Implementers should consider testing
   their design (including the interworking between the payload format
   implementation and the core video codec) using the tools provided by
   ITU-T/ISO/IEC, for example, conformance bitstreams as specified in
   [H.265.1].  Not doing so has historically led to systems that perform
   badly and that are not secure.

   Conceptually, both H.264 and HEVC include a Video Coding Layer (VCL),
   which is often used to refer to the coding-tool features, and a
   Network Abstraction Layer (NAL), which is often used to refer to the
   systems and transport interface aspects of the codecs.

1.1.1.  Coding-Tool Features

   Similar to earlier hybrid-video-coding-based standards, including
   H.264, the following basic video coding design is employed by HEVC.
   A prediction signal is first formed by either intra- or motion-
   compensated prediction, and the residual (the difference between the
   original and the prediction) is then coded.  The gains in coding
   efficiency are achieved by redesigning and improving almost all parts
   of the codec over earlier designs.  In addition, HEVC includes
   several tools to make the implementation on parallel architectures
   easier.  Below is a summary of HEVC coding-tool features.

   Quad-tree block and transform structure

   One of the major tools that contributes significantly to the coding
   efficiency of HEVC is the use of flexible coding blocks and
   transforms, which are defined in a hierarchical quad-tree manner.
   Unlike H.264, where the basic coding block is a macroblock of fixed-
   size 16x16, HEVC defines a Coding Tree Unit (CTU) of a maximum size
   of 64x64.  Each CTU can be divided into smaller units in a
   hierarchical quad-tree manner and can represent smaller blocks down
   to size 4x4.  Similarly, the transforms used in HEVC can have
   different sizes, starting from 4x4 and going up to 32x32.  Utilizing
   large blocks and transforms contributes to the major gain of HEVC,
   especially at high resolutions.







Wang, et al.                 Standards Track                    [Page 4]

RFC 7798               RTP Payload Format for HEVC            March 2016


   Entropy coding

   HEVC uses a single entropy-coding engine, which is based on Context
   Adaptive Binary Arithmetic Coding (CABAC) [CABAC], whereas H.264 uses
   two distinct entropy coding engines.  CABAC in HEVC shares many
   similarities with CABAC of H.264, but contains several improvements.
   Those include improvements in coding efficiency and lowered
   implementation complexity, especially for parallel architectures.

   In-loop filtering

   H.264 includes an in-loop adaptive deblocking filter, where the
   blocking artifacts around the transform edges in the reconstructed
   picture are smoothed to improve the picture quality and compression
   efficiency.  In HEVC, a similar deblocking filter is employed but
   with somewhat lower complexity.  In addition, pictures undergo a
   subsequent filtering operation called Sample Adaptive Offset (SAO),
   which is a new design element in HEVC.  SAO basically adds a pixel-
   level offset in an adaptive manner and usually acts as a de-ringing
   filter.  It is observed that SAO improves the picture quality,
   especially around sharp edges, contributing substantially to visual
   quality improvements of HEVC.

   Motion prediction and coding

   There have been a number of improvements in this area that are
   summarized as follows.  The first category is motion merge and
   Advanced Motion Vector Prediction (AMVP) modes.  The motion
   information of a prediction block can be inferred from the spatially
   or temporally neighboring blocks.  This is similar to the DIRECT mode
   in H.264 but includes new aspects to incorporate the flexible quad-
   tree structure and methods to improve the parallel implementations.
   In addition, the motion vector predictor can be signaled for improved
   efficiency.  The second category is high-precision interpolation.
   The interpolation filter length is increased to 8-tap from 6-tap,
   which improves the coding efficiency but also comes with increased
   complexity.  In addition, the interpolation filter is defined with
   higher precision without any intermediate rounding operations to
   further improve the coding efficiency.

   Intra prediction and intra-coding

   Compared to 8 intra prediction modes in H.264, HEVC supports angular
   intra prediction with 33 directions.  This increased flexibility
   improves both objective coding efficiency and visual quality as the
   edges can be better predicted and ringing artifacts around the edges
   can be reduced.  In addition, the reference samples are adaptively
   smoothed based on the prediction direction.  To avoid contouring



Wang, et al.                 Standards Track                    [Page 5]

RFC 7798               RTP Payload Format for HEVC            March 2016


   artifacts a new interpolative prediction generation is included to
   improve the visual quality.  Furthermore, Discrete Sine Transform
   (DST) is utilized instead of traditional Discrete Cosine Transform
   (DCT) for 4x4 intra-transform blocks.

   Other coding-tool features

   HEVC includes some tools for lossless coding and efficient screen-
   content coding, such as skipping the transform for certain blocks.
   These tools are particularly useful, for example, when streaming the
   user interface of a mobile device to a large display.

1.1.2.  Systems and Transport Interfaces

   HEVC inherited the basic systems and transport interfaces designs
   from H.264.  These include the NAL-unit-based syntax structure, the
   hierarchical syntax and data unit structure, the Supplemental
   Enhancement Information (SEI) message mechanism, and the video
   buffering model based on the Hypothetical Reference Decoder (HRD).
   The hierarchical syntax and data unit structure consists of sequence-
   level parameter sets, multi-picture-level or picture-level parameter
   sets, slice-level header parameters, and lower-level parameters.  In
   the following, a list of differences in these aspects compared to
   H.264 is summarized.

   Video parameter set

   A new type of parameter set, called Video Parameter Set (VPS), was
   introduced.  For the first (2013) version of [HEVC], the VPS NAL unit
   is required to be available prior to its activation, while the
   information contained in the VPS is not necessary for operation of
   the decoding process.  For future HEVC extensions, such as the 3D or
   scalable extensions, the VPS is expected to include information
   necessary for operation of the decoding process, e.g., decoding
   dependency or information for reference picture set construction of
   enhancement layers.  The VPS provides a "big picture" of a bitstream,
   including what types of operation points are provided, the profile,
   tier, and level of the operation points, and some other high-level
   properties of the bitstream that can be used as the basis for session
   negotiation and content selection, etc. (see Section 7.1).

   Profile, tier, and level

   The profile, tier, and level syntax structure that can be included in
   both the VPS and Sequence Parameter Set (SPS) includes 12 bytes of
   data to describe the entire bitstream (including all temporally
   scalable layers, which are referred to as sub-layers in the HEVC
   specification), and can optionally include more profile, tier, and



Wang, et al.                 Standards Track                    [Page 6]

RFC 7798               RTP Payload Format for HEVC            March 2016


   level information pertaining to individual temporally scalable
   layers.  The profile indicator shows the "best viewed as" profile
   when the bitstream conforms to multiple profiles, similar to the
   major brand concept in the ISO Base Media File Format (ISOBMFF)
   [IS014496-12] [IS015444-12] and file formats derived based on
   ISOBMFF, such as the 3GPP file format [3GPPFF].  The profile, tier,
   and level syntax structure also includes indications such as 1)
   whether the bitstream is free of frame-packed content, 2) whether the
   bitstream is free of interlaced source content, and 3) whether the
   bitstream is free of field pictures.  When the answer is yes for both
   2) and 3), the bitstream contains only frame pictures of progressive
   source.  Based on these indications, clients/players without support
   of post-processing functionalities for the handling of frame-packed,
   interlaced source content or field pictures can reject those
   bitstreams that contain such pictures.

   Bitstream and elementary stream

   HEVC includes a definition of an elementary stream, which is new
   compared to H.264.  An elementary stream consists of a sequence of
   one or more bitstreams.  An elementary stream that consists of two or
   more bitstreams has typically been formed by splicing together two or
   more bitstreams (or parts thereof).  When an elementary stream
   contains more than one bitstream, the last NAL unit of the last
   access unit of a bitstream (except the last bitstream in the
   elementary stream) must contain an end of bitstream NAL unit, and the
   first access unit of the subsequent bitstream must be an Intra-Random
   Access Point (IRAP) access unit.  This IRAP access unit may be a
   Clean Random Access (CRA), Broken Link Access (BLA), or Instantaneous
   Decoding Refresh (IDR) access unit.

   Random access support

   HEVC includes signaling in the NAL unit header, through NAL unit
   types, of IRAP pictures beyond IDR pictures.  Three types of IRAP
   pictures, namely IDR, CRA, and BLA pictures, are supported: IDR
   pictures are conventionally referred to as closed group-of-pictures
   (closed-GOP) random access points whereas CRA and BLA pictures are
   conventionally referred to as open-GOP random access points.  BLA
   pictures usually originate from splicing of two bitstreams or part
   thereof at a CRA picture, e.g., during stream switching.  To enable
   better systems usage of IRAP pictures, altogether six different NAL
   units are defined to signal the properties of the IRAP pictures,
   which can be used to better match the stream access point types as
   defined in the ISOBMFF [IS014496-12] [IS015444-12], which are
   utilized for random access support in both 3GP-DASH [3GPDASH] and
   MPEG DASH [MPEGDASH].  Pictures following an IRAP picture in decoding
   order and preceding the IRAP picture in output order are referred to



Wang, et al.                 Standards Track                    [Page 7]

RFC 7798               RTP Payload Format for HEVC            March 2016


   as leading pictures associated with the IRAP picture.  There are two
   types of leading pictures: Random Access Decodable Leading (RADL)
   pictures and Random Access Skipped Leading (RASL) pictures.  RADL
   pictures are decodable when the decoding started at the associated
   IRAP picture; RASL pictures are not decodable when the decoding
   started at the associated IRAP picture and are usually discarded.
   HEVC provides mechanisms to enable specifying the conformance of a
   bitstream wherein the originally present RASL pictures have been
   discarded.  Consequently, system components can discard RASL
   pictures, when needed, without worrying about causing the bitstream
   to become non-compliant.

   Temporal scalability support

   HEVC includes an improved support of temporal scalability, by
   inclusion of the signaling of TemporalId in the NAL unit header, the
   restriction that pictures of a particular temporal sub-layer cannot
   be used for inter prediction reference by pictures of a lower
   temporal sub-layer, the sub-bitstream extraction process, and the
   requirement that each sub-bitstream extraction output be a conforming
   bitstream.  Media-Aware Network Elements (MANEs) can utilize the
   TemporalId in the NAL unit header for stream adaptation purposes
   based on temporal scalability.

   Temporal sub-layer switching support

   HEVC specifies, through NAL unit types present in the NAL unit
   header, the signaling of Temporal Sub-layer Access (TSA) and Step-
   wise Temporal Sub-layer Access (STSA).  A TSA picture and pictures
   following the TSA picture in decoding order do not use pictures prior
   to the TSA picture in decoding order with TemporalId greater than or
   equal to that of the TSA picture for inter prediction reference.  A
   TSA picture enables up-switching, at the TSA picture, to the sub-
   layer containing the TSA picture or any higher sub-layer, from the
   immediately lower sub-layer.  An STSA picture does not use pictures
   with the same TemporalId as the STSA picture for inter prediction
   reference.  Pictures following an STSA picture in decoding order with
   the same TemporalId as the STSA picture do not use pictures prior to
   the STSA picture in decoding order with the same TemporalId as the
   STSA picture for inter prediction reference.  An STSA picture enables
   up-switching, at the STSA picture, to the sub-layer containing the
   STSA picture, from the immediately lower sub-layer.

   Sub-layer reference or non-reference pictures

   The concept and signaling of reference/non-reference pictures in HEVC
   are different from H.264.  In H.264, if a picture may be used by any
   other picture for inter prediction reference, it is a reference



Wang, et al.                 Standards Track                    [Page 8]

RFC 7798               RTP Payload Format for HEVC            March 2016


   picture; otherwise, it is a non-reference picture, and this is
   signaled by two bits in the NAL unit header.  In HEVC, a picture is
   called a reference picture only when it is marked as "used for
   reference".  In addition, the concept of sub-layer reference picture
   was introduced.  If a picture may be used by another other picture
   with the same TemporalId for inter prediction reference, it is a sub-
   layer reference picture; otherwise, it is a sub-layer non-reference
   picture.  Whether a picture is a sub-layer reference picture or sub-
   layer non-reference picture is signaled through NAL unit type values.

   Extensibility

   Besides the TemporalId in the NAL unit header, HEVC also includes the
   signaling of a six-bit layer ID in the NAL unit header, which must be
   equal to 0 for a single-layer bitstream.  Extension mechanisms have
   been included in the VPS, SPS, Picture Parameter Set (PPS), SEI NAL
   unit, slice headers, and so on.  All these extension mechanisms
   enable future extensions in a backward-compatible manner, such that
   bitstreams encoded according to potential future HEVC extensions can
   be fed to then-legacy decoders (e.g., HEVC version 1 decoders), and
   the then-legacy decoders can decode and output the base-layer
   bitstream.

   Bitstream extraction

   HEVC includes a bitstream-extraction process as an integral part of
   the overall decoding process.  The bitstream extraction process is
   used in the process of bitstream conformance tests, which is part of
   the HRD buffering model.

   Reference picture management

   The reference picture management of HEVC, including reference picture
   marking and removal from the Decoded Picture Buffer (DPB) as well as
   Reference Picture List Construction (RPLC), differs from that of
   H.264.  Instead of the reference picture marking mechanism based on a
   sliding window plus adaptive Memory Management Control Operation
   (MMCO) described in H.264, HEVC specifies a reference picture
   management and marking mechanism based on Reference Picture Set
   (RPS), and the RPLC is consequently based on the RPS mechanism.  An
   RPS consists of a set of reference pictures associated with a
   picture, consisting of all reference pictures that are prior to the
   associated picture in decoding order, that may be used for inter
   prediction of the associated picture or any picture following the
   associated picture in decoding order.  The reference picture set
   consists of five lists of reference pictures; RefPicSetStCurrBefore,
   RefPicSetStCurrAfter, RefPicSetStFoll, RefPicSetLtCurr, and
   RefPicSetLtFoll.  RefPicSetStCurrBefore, RefPicSetStCurrAfter, and



Wang, et al.                 Standards Track                    [Page 9]

RFC 7798               RTP Payload Format for HEVC            March 2016


   RefPicSetLtCurr contain all reference pictures that may be used in
   inter prediction of the current picture and that may be used in inter
   prediction of one or more of the pictures following the current
   picture in decoding order.  RefPicSetStFoll and RefPicSetLtFoll
   consist of all reference pictures that are not used in inter
   prediction of the current picture but may be used in inter prediction
   of one or more of the pictures following the current picture in
   decoding order.  RPS provides an "intra-coded" signaling of the DPB
   status, instead of an "inter-coded" signaling, mainly for improved
   error resilience.  The RPLC process in HEVC is based on the RPS, by
   signaling an index to an RPS subset for each reference index; this
   process is simpler than the RPLC process in H.264.

   Ultra-low delay support

   HEVC specifies a sub-picture-level HRD operation, for support of the
   so-called ultra-low delay.  The mechanism specifies a standard-
   compliant way to enable delay reduction below a one-picture interval.
   Coded Picture Buffer (CPB) and DPB parameters at the sub-picture
   level may be signaled, and utilization of this information for the
   derivation of CPB timing (wherein the CPB removal time corresponds to
   decoding time) and DPB output timing (display time) is specified.
   Decoders are allowed to operate the HRD at the conventional access-
   unit level, even when the sub-picture-level HRD parameters are
   present.

   New SEI messages

   HEVC inherits many H.264 SEI messages with changes in syntax and/or
   semantics making them applicable to HEVC.  Additionally, there are a
   few new SEI messages reviewed briefly in the following paragraphs.

   The display orientation SEI message informs the decoder of a
   transformation that is recommended to be applied to the cropped
   decoded picture prior to display, such that the pictures can be
   properly displayed, e.g., in an upside-up manner.

   The structure of pictures SEI message provides information on the NAL
   unit types, picture-order count values, and prediction dependencies
   of a sequence of pictures.  The SEI message can be used, for example,
   for concluding what impact a lost picture has on other pictures.

   The decoded picture hash SEI message provides a checksum derived from
   the sample values of a decoded picture.  It can be used for detecting
   whether a picture was correctly received and decoded.






Wang, et al.                 Standards Track                   [Page 10]

RFC 7798               RTP Payload Format for HEVC            March 2016


   The active parameter sets SEI message includes the IDs of the active
   video parameter set and the active sequence parameter set and can be
   used to activate VPSs and SPSs.  In addition, the SEI message
   includes the following indications: 1) An indication of whether "full
   random accessibility" is supported (when supported, all parameter
   sets needed for decoding of the remaining of the bitstream when
   random accessing from the beginning of the current CVS by completely
   discarding all access units earlier in decoding order are present in
   the remaining bitstream, and all coded pictures in the remaining
   bitstream can be correctly decoded); 2) An indication of whether
   there is no parameter set within the current CVS that updates another
   parameter set of the same type preceding in decoding order.  An
   update of a parameter set refers to the use of the same parameter set
   ID but with some other parameters changed.  If this property is true
   for all CVSs in the bitstream, then all parameter sets can be sent
   out-of-band before session start.

   The decoding unit information SEI message provides information
   regarding coded picture buffer removal delay for a decoding unit.
   The message can be used in very-low-delay buffering operations.

   The region refresh information SEI message can be used together with
   the recovery point SEI message (present in both H.264 and HEVC) for
   improved support of gradual decoding refresh.  This supports random
   access from inter-coded pictures, wherein complete pictures can be
   correctly decoded or recovered after an indicated number of pictures
   in output/display order.

1.1.3.  Parallel Processing Support

   The reportedly significantly higher encoding computational demand of
   HEVC over H.264, in conjunction with the ever-increasing video
   resolution (both spatially and temporally) required by the market,
   led to the adoption of VCL coding tools specifically targeted to
   allow for parallelization on the sub-picture level.  That is,
   parallelization occurs, at the minimum, at the granularity of an
   integer number of CTUs.  The targets for this type of high-level
   parallelization are multicore CPUs and DSPs as well as multiprocessor
   systems.  In a system design, to be useful, these tools require
   signaling support, which is provided in Section 7 of this memo.  This
   section provides a brief overview of the tools available in [HEVC].

   Many of the tools incorporated in HEVC were designed keeping in mind
   the potential parallel implementations in multicore/multiprocessor
   architectures.  Specifically, for parallelization, four picture
   partition strategies, as described below, are available.





Wang, et al.                 Standards Track                   [Page 11]

RFC 7798               RTP Payload Format for HEVC            March 2016


   Slices are segments of the bitstream that can be reconstructed
   independently from other slices within the same picture (though there
   may still be interdependencies through loop filtering operations).
   Slices are the only tool that can be used for parallelization that is
   also available, in virtually identical form, in H.264.
   Parallelization based on slices does not require much inter-processor
   or inter-core communication (except for inter-processor or inter-core
   data sharing for motion compensation when decoding a predictively
   coded picture, which is typically much heavier than inter-processor
   or inter-core data sharing due to in-picture prediction), as slices
   are designed to be independently decodable.  However, for the same
   reason, slices can require some coding overhead.  Further, slices (in
   contrast to some of the other tools mentioned below) also serve as
   the key mechanism for bitstream partitioning to match Maximum
   Transfer Unit (MTU) size requirements, due to the in-picture
   independence of slices and the fact that each regular slice is
   encapsulated in its own NAL unit.  In many cases, the goal of
   parallelization and the goal of MTU size matching can place
   contradicting demands to the slice layout in a picture.  The
   realization of this situation led to the development of the more
   advanced tools mentioned below.

   Dependent slice segments allow for fragmentation of a coded slice
   into fragments at CTU boundaries without breaking any in-picture
   prediction mechanisms.  They are complementary to the fragmentation
   mechanism described in this memo in that they need the cooperation of
   the encoder.  As a dependent slice segment necessarily contains an
   integer number of CTUs, a decoder using multiple cores operating on
   CTUs can process a dependent slice segment without communicating
   parts of the slice segment's bitstream to other cores.
   Fragmentation, as specified in this memo, in contrast, does not
   guarantee that a fragment contains an integer number of CTUs.

   In Wavefront Parallel Processing (WPP), the picture is partitioned
   into rows of CTUs.  Entropy decoding and prediction are allowed to
   use data from CTUs in other partitions.  Parallel processing is
   possible through parallel decoding of CTU rows, where the start of
   the decoding of a row is delayed by two CTUs, so to ensure that data
   related to a CTU above and to the right of the subject CTU is
   available before the subject CTU is being decoded.  Using this
   staggered start (which appears like a wavefront when represented
   graphically), parallelization is possible with up to as many
   processors/cores as the picture contains CTU rows.

   Because in-picture prediction between neighboring CTU rows within a
   picture is allowed, the required inter-processor/inter-core
   communication to enable in-picture prediction can be substantial.
   The WPP partitioning does not result in the creation of more NAL



Wang, et al.                 Standards Track                   [Page 12]

RFC 7798               RTP Payload Format for HEVC            March 2016


   units compared to when it is not applied; thus, WPP cannot be used
   for MTU size matching, though slices can be used in combination for
   that purpose.

   Tiles define horizontal and vertical boundaries that partition a
   picture into tile columns and rows.  The scan order of CTUs is
   changed to be local within a tile (in the order of a CTU raster scan
   of a tile), before decoding the top-left CTU of the next tile in the
   order of tile raster scan of a picture.  Similar to slices, tiles
   break in-picture prediction dependencies (including entropy decoding
   dependencies).  However, they do not need to be included into
   individual NAL units (same as WPP in this regard); hence, tiles
   cannot be used for MTU size matching, though slices can be used in
   combination for that purpose.  Each tile can be processed by one
   processor/core, and the inter-processor/inter-core communication
   required for in-picture prediction between processing units decoding
   neighboring tiles is limited to conveying the shared slice header in
   cases a slice is spanning more than one tile, and loop-filtering-
   related sharing of reconstructed samples and metadata.  Insofar,
   tiles are less demanding in terms of inter-processor communication
   bandwidth compared to WPP due to the in-picture independence between
   two neighboring partitions.

1.1.4.  NAL Unit Header

   HEVC maintains the NAL unit concept of H.264 with modifications.
   HEVC uses a two-byte NAL unit header, as shown in Figure 1.  The
   payload of a NAL unit refers to the NAL unit excluding the NAL unit
   header.

            +---------------+---------------+
            |0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7|
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |F|   Type    |  LayerId  | TID |
            +-------------+-----------------+

   Figure 1: The Structure of the HEVC NAL Unit Header

   The semantics of the fields in the NAL unit header are as specified
   in [HEVC] and described briefly below for convenience.  In addition
   to the name and size of each field, the corresponding syntax element
   name in [HEVC] is also provided.

   F: 1 bit
      forbidden_zero_bit.  Required to be zero in [HEVC].  Note that the
      inclusion of this bit in the NAL unit header was to enable
      transport of HEVC video over MPEG-2 transport systems (avoidance
      of start code emulations) [MPEG2S].  In the context of this memo,



Wang, et al.                 Standards Track                   [Page 13]

RFC 7798               RTP Payload Format for HEVC            March 2016


      the value 1 may be used to indicate a syntax violation, e.g., for
      a NAL unit resulted from aggregating a number of fragmented units
      of a NAL unit but missing the last fragment, as described in
      Section 4.4.3.

   Type: 6 bits
      nal_unit_type.  This field specifies the NAL unit type as defined
      in Table 7-1 of [HEVC].  If the most significant bit of this field
      of a NAL unit is equal to 0 (i.e., the value of this field is less
      than 32), the NAL unit is a VCL NAL unit.  Otherwise, the NAL unit
      is a non-VCL NAL unit.  For a reference of all currently defined
      NAL unit types and their semantics, please refer to Section 7.4.2
      in [HEVC].

   LayerId: 6 bits
      nuh_layer_id.  Required to be equal to zero in [HEVC].  It is
      anticipated that in future scalable or 3D video coding extensions
      of this specification, this syntax element will be used to
      identify additional layers that may be present in the CVS, wherein
      a layer may be, e.g., a spatial scalable layer, a quality scalable
      layer, a texture view, or a depth view.

   TID: 3 bits
      nuh_temporal_id_plus1.  This field specifies the temporal
      identifier of the NAL unit plus 1.  The value of TemporalId is
      equal to TID minus 1.  A TID value of 0 is illegal to ensure that
      there is at least one bit in the NAL unit header equal to 1, so to
      enable independent considerations of start code emulations in the
      NAL unit header and in the NAL unit payload data.

1.2.  Overview of the Payload Format

   This payload format defines the following processes required for
   transport of HEVC coded data over RTP [RFC3550]:

   o  Usage of RTP header with this payload format

   o  Packetization of HEVC coded NAL units into RTP packets using three
      types of payload structures: a single NAL unit packet, aggregation
      packet, and fragment unit

   o  Transmission of HEVC NAL units of the same bitstream within a
      single RTP stream or multiple RTP streams (within one or more RTP
      sessions), where within an RTP stream transmission of NAL units
      may be either non-interleaved (i.e., the transmission order of NAL
      units is the same as their decoding order) or interleaved (i.e.,
      the transmission order of NAL units is different from the decoding
      order)



Wang, et al.                 Standards Track                   [Page 14]

RFC 7798               RTP Payload Format for HEVC            March 2016


   o  Media type parameters to be used with the Session Description
      Protocol (SDP) [RFC4566]

   o  A payload header extension mechanism and data structures for
      enhanced support of temporal scalability based on that extension
      mechanism.

2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14 [RFC2119].

   In this document, the above key words will convey that interpretation
   only when in ALL CAPS.  Lowercase uses of these words are not to be
   interpreted as carrying the significance described in RFC 2119.

   This specification uses the notion of setting and clearing a bit when
   bit fields are handled.  Setting a bit is the same as assigning that
   bit the value of 1 (On).  Clearing a bit is the same as assigning
   that bit the value of 0 (Off).

3.  Definitions and Abbreviations

3.1.  Definitions

   This document uses the terms and definitions of [HEVC].  Section
   3.1.1 lists relevant definitions from [HEVC] for convenience.
   Section 3.1.2 provides definitions specific to this memo.

3.1.1.  Definitions from the HEVC Specification

   access unit: A set of NAL units that are associated with each other
   according to a specified classification rule, that are consecutive in
   decoding order, and that contain exactly one coded picture.

   BLA access unit: An access unit in which the coded picture is a BLA
   picture.

   BLA picture: An IRAP picture for which each VCL NAL unit has
   nal_unit_type equal to BLA_W_LP, BLA_W_RADL, or BLA_N_LP.

   Coded Video Sequence (CVS): A sequence of access units that consists,
   in decoding order, of an IRAP access unit with NoRaslOutputFlag equal
   to 1, followed by zero or more access units that are not IRAP access
   units with NoRaslOutputFlag equal to 1, including all subsequent
   access units up to but not including any subsequent access unit that
   is an IRAP access unit with NoRaslOutputFlag equal to 1.



Wang, et al.                 Standards Track                   [Page 15]

RFC 7798               RTP Payload Format for HEVC            March 2016


      Informative note: An IRAP access unit may be an IDR access unit, a
      BLA access unit, or a CRA access unit.  The value of
      NoRaslOutputFlag is equal to 1 for each IDR access unit, each BLA
      access unit, and each CRA access unit that is the first access
      unit in the bitstream in decoding order, is the first access unit
      that follows an end of sequence NAL unit in decoding order, or has
      HandleCraAsBlaFlag equal to 1.

   CRA access unit: An access unit in which the coded picture is a CRA
   picture.

   CRA picture: A RAP picture for which each VCL NAL unit has
   nal_unit_type equal to CRA_NUT.

   IDR access unit: An access unit in which the coded picture is an IDR
   picture.

   IDR picture: A RAP picture for which each VCL NAL unit has
   nal_unit_type equal to IDR_W_RADL or IDR_N_LP.

   IRAP access unit: An access unit in which the coded picture is an
   IRAP picture.

   IRAP picture: A coded picture for which each VCL NAL unit has
   nal_unit_type in the range of BLA_W_LP (16) to RSV_IRAP_VCL23 (23),
   inclusive.

   layer: A set of VCL NAL units that all have a particular value of
   nuh_layer_id and the associated non-VCL NAL units, or one of a set of
   syntactical structures having a hierarchical relationship.

   operation point: bitstream created from another bitstream by
   operation of the sub-bitstream extraction process with the another
   bitstream, a target highest TemporalId, and a target-layer identifier
   list as input.

   random access: The act of starting the decoding process for a
   bitstream at a point other than the beginning of the bitstream.

   sub-layer: A temporal scalable layer of a temporal scalable bitstream
   consisting of VCL NAL units with a particular value of the TemporalId
   variable, and the associated non-VCL NAL units.

   sub-layer representation: A subset of the bitstream consisting of NAL
   units of a particular sub-layer and the lower sub-layers.

   tile: A rectangular region of coding tree blocks within a particular
   tile column and a particular tile row in a picture.



Wang, et al.                 Standards Track                   [Page 16]

RFC 7798               RTP Payload Format for HEVC            March 2016


   tile column: A rectangular region of coding tree blocks having a
   height equal to the height of the picture and a width specified by
   syntax elements in the picture parameter set.

   tile row: A rectangular region of coding tree blocks having a height
   specified by syntax elements in the picture parameter set and a width
   equal to the width of the picture.

3.1.2.  Definitions Specific to This Memo

   dependee RTP stream: An RTP stream on which another RTP stream
   depends.  All RTP streams in a Multiple RTP streams on a Single media
   Transport (MRST) or Multiple RTP streams on Multiple media Transports
   (MRMT), except for the highest RTP stream, are dependee RTP streams.

   highest RTP stream: The RTP stream on which no other RTP stream
   depends.  The RTP stream in a Single RTP stream on a Single media
   Transport (SRST) is the highest RTP stream.

   Media-Aware Network Element (MANE): A network element, such as a
   middlebox, selective forwarding unit, or application-layer gateway
   that is capable of parsing certain aspects of the RTP payload headers
   or the RTP payload and reacting to their contents.

      Informative note: The concept of a MANE goes beyond normal routers
      or gateways in that a MANE has to be aware of the signaling (e.g.,
      to learn about the payload type mappings of the media streams),
      and in that it has to be trusted when working with Secure RTP
      (SRTP).  The advantage of using MANEs is that they allow packets
      to be dropped according to the needs of the media coding.  For
      example, if a MANE has to drop packets due to congestion on a
      certain link, it can identify and remove those packets whose
      elimination produces the least adverse effect on the user
      experience.  After dropping packets, MANEs must rewrite RTCP
      packets to match the changes to the RTP stream, as specified in
      Section 7 of [RFC3550].

   Media Transport: As used in the MRST, MRMT, and SRST definitions
   below, Media Transport denotes the transport of packets over a
   transport association identified by a 5-tuple (source address, source
   port, destination address, destination port, transport protocol).
   See also Section 2.1.13 of [RFC7656].

      Informative note: The term "bitstream" in this document is
      equivalent to the term "encoded stream" in [RFC7656].






Wang, et al.                 Standards Track                   [Page 17]

RFC 7798               RTP Payload Format for HEVC            March 2016


   Multiple RTP streams on a Single media Transport (MRST):  Multiple
   RTP streams carrying a single HEVC bitstream on a Single Transport.
   See also Section 3.5 of [RFC7656].

   Multiple RTP streams on Multiple media Transports (MRMT):  Multiple
   RTP streams carrying a single HEVC bitstream on Multiple Transports.
   See also Section 3.5 of [RFC7656].

   NAL unit decoding order: A NAL unit order that conforms to the
   constraints on NAL unit order given in Section 7.4.2.4 in [HEVC].

   NAL unit output order: A NAL unit order in which NAL units of
   different access units are in the output order of the decoded
   pictures corresponding to the access units, as specified in [HEVC],
   and in which NAL units within an access unit are in their decoding
   order.

   NAL-unit-like structure: A data structure that is similar to NAL
   units in the sense that it also has a NAL unit header and a payload,
   with a difference that the payload does not follow the start code
   emulation prevention mechanism required for the NAL unit syntax as
   specified in Section 7.3.1.1 of [HEVC].  Examples of NAL-unit-like
   structures defined in this memo are packet payloads of Aggregation
   Packet (AP), PAyload Content Information (PACI), and Fragmentation
   Unit (FU) packets.

   NALU-time: The value that the RTP timestamp would have if the NAL
   unit would be transported in its own RTP packet.

   RTP stream: See [RFC7656].  Within the scope of this memo, one RTP
   stream is utilized to transport one or more temporal sub-layers.

   Single RTP stream on a Single media Transport (SRST):  Single RTP
   stream carrying a single HEVC bitstream on a Single (Media)
   Transport.  See also Section 3.5 of [RFC7656].

   transmission order: The order of packets in ascending RTP sequence
   number order (in modulo arithmetic).  Within an aggregation packet,
   the NAL unit transmission order is the same as the order of
   appearance of NAL units in the packet.











Wang, et al.                 Standards Track                   [Page 18]

RFC 7798               RTP Payload Format for HEVC            March 2016


3.2.  Abbreviations

   AP       Aggregation Packet

   BLA      Broken Link Access

   CRA      Clean Random Access

   CTB      Coding Tree Block

   CTU      Coding Tree Unit

   CVS      Coded Video Sequence

   DPH      Decoded Picture Hash

   FU       Fragmentation Unit

   HRD      Hypothetical Reference Decoder

   IDR      Instantaneous Decoding Refresh

   IRAP     Intra Random Access Point

   MANE     Media-Aware Network Element

   MRMT     Multiple RTP streams on Multiple media Transports

   MRST     Multiple RTP streams on a Single media Transport

   MTU      Maximum Transfer Unit

   NAL      Network Abstraction Layer

   NALU     Network Abstraction Layer Unit

   PACI     PAyload Content Information

   PHES     Payload Header Extension Structure

   PPS      Picture Parameter Set

   RADL     Random Access Decodable Leading (Picture)

   RASL     Random Access Skipped Leading (Picture)

   RPS      Reference Picture Set




Wang, et al.                 Standards Track                   [Page 19]

RFC 7798               RTP Payload Format for HEVC            March 2016


   SEI      Supplemental Enhancement Information

   SPS      Sequence Parameter Set

   SRST     Single RTP stream on a Single media Transport

   STSA     Step-wise Temporal Sub-layer Access

   TSA      Temporal Sub-layer Access

   TSCI     Temporal Scalability Control Information

   VCL      Video Coding Layer

   VPS      Video Parameter Set

4.  RTP Payload Format

4.1.  RTP Header Usage

   The format of the RTP header is specified in [RFC3550] (reprinted as
   Figure 2 for convenience).  This payload format uses the fields of
   the header in a manner consistent with that specification.

   The RTP payload (and the settings for some RTP header bits) for
   aggregation packets and fragmentation units are specified in Sections
   4.4.2 and 4.4.3, respectively.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |V=2|P|X|  CC   |M|     PT      |       sequence number         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           timestamp                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           synchronization source (SSRC) identifier            |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |            contributing source (CSRC) identifiers             |
   |                             ....                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 2: RTP Header According to [RFC3550]









Wang, et al.                 Standards Track                   [Page 20]

RFC 7798               RTP Payload Format for HEVC            March 2016


   The RTP header information to be set according to this RTP payload
   format is set as follows:

   Marker bit (M): 1 bit

      Set for the last packet of the access unit, carried in the current
      RTP stream.  This is in line with the normal use of the M bit in
      video formats to allow an efficient playout buffer handling.  When
      MRST or MRMT is in use, if an access unit appears in multiple RTP
      streams, the marker bit is set on each RTP stream's last packet of
      the access unit.

         Informative note: The content of a NAL unit does not tell
         whether or not the NAL unit is the last NAL unit, in decoding
         order, of an access unit.  An RTP sender implementation may
         obtain this information from the video encoder.  If, however,
         the implementation cannot obtain this information directly from
         the encoder, e.g., when the bitstream was pre-encoded, and also
         there is no timestamp allocated for each NAL unit, then the
         sender implementation can inspect subsequent NAL units in
         decoding order to determine whether or not the NAL unit is the
         last NAL unit of an access unit as follows.  A NAL unit is
         determined to be the last NAL unit of an access unit if it is
         the last NAL unit of the bitstream.  A NAL unit naluX is also
         determined to be the last NAL unit of an access unit if both
         the following conditions are true: 1) the next VCL NAL unit
         naluY in decoding order has the high-order bit of the first
         byte after its NAL unit header equal to 1, and 2) all NAL units
         between naluX and naluY, when present, have nal_unit_type in
         the range of 32 to 35, inclusive, equal to 39, or in the ranges
         of 41 to 44, inclusive, or 48 to 55, inclusive.

   Payload Type (PT): 7 bits

      The assignment of an RTP payload type for this new packet format
      is outside the scope of this document and will not be specified
      here.  The assignment of a payload type has to be performed either
      through the profile used or in a dynamic way.

         Informative note: It is not required to use different payload
         type values for different RTP streams in MRST or MRMT.

   Sequence Number (SN): 16 bits

      Set and used in accordance with [RFC3550].






Wang, et al.                 Standards Track                   [Page 21]

RFC 7798               RTP Payload Format for HEVC            March 2016


   Timestamp: 32 bits

      The RTP timestamp is set to the sampling timestamp of the content.
      A 90 kHz clock rate MUST be used.

      If the NAL unit has no timing properties of its own (e.g.,
      parameter set and SEI NAL units), the RTP timestamp MUST be set to
      the RTP timestamp of the coded picture of the access unit in which
      the NAL unit (according to Section 7.4.2.4.4 of [HEVC]) is
      included.

      Receivers MUST use the RTP timestamp for the display process, even
      when the bitstream contains picture timing SEI messages or
      decoding unit information SEI messages as specified in [HEVC].
      However, this does not mean that picture timing SEI messages in
      the bitstream should be discarded, as picture timing SEI messages
      may contain frame-field information that is important in
      appropriately rendering interlaced video.

   Synchronization source (SSRC): 32 bits

      Used to identify the source of the RTP packets.  When using SRST,
      by definition a single SSRC is used for all parts of a single
      bitstream.  In MRST or MRMT, different SSRCs are used for each RTP
      stream containing a subset of the sub-layers of the single
      (temporally scalable) bitstream.  A receiver is required to
      correctly associate the set of SSRCs that are included parts of
      the same bitstream.

4.2.  Payload Header Usage

   The first two bytes of the payload of an RTP packet are referred to
   as the payload header.  The payload header consists of the same
   fields (F, Type, LayerId, and TID) as the NAL unit header as shown in
   Section 1.1.4, irrespective of the type of the payload structure.

   The TID value indicates (among other things) the relative importance
   of an RTP packet, for example, because NAL units belonging to higher
   temporal sub-layers are not used for the decoding of lower temporal
   sub-layers.  A lower value of TID indicates a higher importance.
   More-important NAL units MAY be better protected against transmission
   losses than less-important NAL units.









Wang, et al.                 Standards Track                   [Page 22]

RFC 7798               RTP Payload Format for HEVC            March 2016


4.3.  Transmission Modes

   This memo enables transmission of an HEVC bitstream over:

      o a Single RTP stream on a Single media Transport (SRST),

      o Multiple RTP streams over a Single media Transport (MRST), or

      o Multiple RTP streams on Multiple media Transports (MRMT).

      Informative note: While this specification enables the use of MRST
      within the H.265 RTP payload, the signaling of MRST within SDP
      offer/answer is not fully specified at the time of this writing.
      See [RFC5576] and [RFC5583] for what is supported today as well as
      [RTP-MULTI-STREAM] and [SDP-NEG] for future directions.

   When in MRMT, the dependency of one RTP stream on another RTP stream
   is typically indicated as specified in [RFC5583].  [RFC5583] can also
   be utilized to specify dependencies within MRST, but only if the RTP
   streams utilize distinct payload types.

   SRST or MRST SHOULD be used for point-to-point unicast scenarios,
   whereas MRMT SHOULD be used for point-to-multipoint multicast
   scenarios where different receivers require different operation
   points of the same HEVC bitstream, to improve bandwidth utilizing
   efficiency.

      Informative note: A multicast may degrade to a unicast after all
      but one receivers have left (this is a justification of the first
      "SHOULD" instead of "MUST"), and there might be scenarios where
      MRMT is desirable but not possible, e.g., when IP multicast is not
      deployed in certain network (this is a justification of the second
      "SHOULD" instead of "MUST").

   The transmission mode is indicated by the tx-mode media parameter
   (see Section 7.1).  If tx-mode is equal to "SRST", SRST MUST be used.
   Otherwise, if tx-mode is equal to "MRST", MRST MUST be used.
   Otherwise (tx-mode is equal to "MRMT"), MRMT MUST be used.

      Informative note: When an RTP stream does not depend on other RTP
      streams, any of SRST, MRST, or MRMT may be in use for the RTP
      stream.

   Receivers MUST support all of SRST, MRST, and MRMT.

      Informative note: The required support of MRMT by receivers does
      not imply that multicast must be supported by receivers.




Wang, et al.                 Standards Track                   [Page 23]

RFC 7798               RTP Payload Format for HEVC            March 2016


4.4.  Payload Structures

   Four different types of RTP packet payload structures are specified.
   A receiver can identify the type of an RTP packet payload through the
   Type field in the payload header.

   The four different payload structures are as follows:

   o  Single NAL unit packet: Contains a single NAL unit in the payload,
      and the NAL unit header of the NAL unit also serves as the payload
      header.  This payload structure is specified in Section 4.4.1.

   o  Aggregation Packet (AP): Contains more than one NAL unit within
      one access unit.  This payload structure is specified in Section
      4.4.2.

   o  Fragmentation Unit (FU): Contains a subset of a single NAL unit.
      This payload structure is specified in Section 4.4.3.

   o  PACI carrying RTP packet: Contains a payload header (that differs
      from other payload headers for efficiency), a Payload Header
      Extension Structure (PHES), and a PACI payload.  This payload
      structure is specified in Section 4.4.4.

4.4.1.  Single NAL Unit Packets

   A single NAL unit packet contains exactly one NAL unit, and consists
   of a payload header (denoted as PayloadHdr), a conditional 16-bit
   DONL field (in network byte order), and the NAL unit payload data
   (the NAL unit excluding its NAL unit header) of the contained NAL
   unit, as shown in Figure 3.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           PayloadHdr          |      DONL (conditional)       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                  NAL unit payload data                        |
   |                                                               |
   |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               :...OPTIONAL RTP padding        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 3: The Structure of a Single NAL Unit Packet






Wang, et al.                 Standards Track                   [Page 24]

RFC 7798               RTP Payload Format for HEVC            March 2016


   The payload header SHOULD be an exact copy of the NAL unit header of
   the contained NAL unit.  However, the Type (i.e., nal_unit_type)
   field MAY be changed, e.g., when it is desirable to handle a CRA
   picture to be a BLA picture [JCTVC-J0107].

   The DONL field, when present, specifies the value of the 16 least
   significant bits of the decoding order number of the contained NAL
   unit.  If sprop-max-don-diff is greater than 0 for any of the RTP
   streams, the DONL field MUST be present, and the variable DON for the
   contained NAL unit is derived as equal to the value of the DONL
   field.  Otherwise (sprop-max-don-diff is equal to 0 for all the RTP
   streams), the DONL field MUST NOT be present.

4.4.2.  Aggregation Packets (APs)

   Aggregation Packets (APs) are introduced to enable the reduction of
   packetization overhead for small NAL units, such as most of the non-
   VCL NAL units, which are often only a few octets in size.

   An AP aggregates NAL units within one access unit.  Each NAL unit to
   be carried in an AP is encapsulated in an aggregation unit.  NAL
   units aggregated in one AP are in NAL unit decoding order.

   An AP consists of a payload header (denoted as PayloadHdr) followed
   by two or more aggregation units, as shown in Figure 4.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    PayloadHdr (Type=48)       |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   |             two or more aggregation units                     |
   |                                                               |
   |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               :...OPTIONAL RTP padding        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 4: The Structure of an Aggregation Packet

   The fields in the payload header are set as follows.  The F bit MUST
   be equal to 0 if the F bit of each aggregated NAL unit is equal to
   zero; otherwise, it MUST be equal to 1.  The Type field MUST be equal
   to 48.  The value of LayerId MUST be equal to the lowest value of
   LayerId of all the aggregated NAL units.  The value of TID MUST be
   the lowest value of TID of all the aggregated NAL units.





Wang, et al.                 Standards Track                   [Page 25]

RFC 7798               RTP Payload Format for HEVC            March 2016


      Informative note: All VCL NAL units in an AP have the same TID
      value since they belong to the same access unit.  However, an AP
      may contain non-VCL NAL units for which the TID value in the NAL
      unit header may be different than the TID value of the VCL NAL
      units in the same AP.

   An AP MUST carry at least two aggregation units and can carry as many
   aggregation units as necessary; however, the total amount of data in
   an AP obviously MUST fit into an IP packet, and the size SHOULD be
   chosen so that the resulting IP packet is smaller than the MTU size
   so to avoid IP layer fragmentation.  An AP MUST NOT contain FUs
   specified in Section 4.4.3.  APs MUST NOT be nested; i.e., an AP must
   not contain another AP.

   The first aggregation unit in an AP consists of a conditional 16-bit
   DONL field (in network byte order) followed by a 16-bit unsigned size
   information (in network byte order) that indicates the size of the
   NAL unit in bytes (excluding these two octets, but including the NAL
   unit header), followed by the NAL unit itself, including its NAL unit
   header, as shown in Figure 5.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   :       DONL (conditional)      |   NALU size   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   NALU size   |                                               |
   +-+-+-+-+-+-+-+-+         NAL unit                              |
   |                                                               |
   |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 5: The Structure of the First Aggregation Unit in an AP

   The DONL field, when present, specifies the value of the 16 least
   significant bits of the decoding order number of the aggregated NAL
   unit.

   If sprop-max-don-diff is greater than 0 for any of the RTP streams,
   the DONL field MUST be present in an aggregation unit that is the
   first aggregation unit in an AP, and the variable DON for the
   aggregated NAL unit is derived as equal to the value of the DONL
   field.  Otherwise (sprop-max-don-diff is equal to 0 for all the RTP
   streams), the DONL field MUST NOT be present in an aggregation unit
   that is the first aggregation unit in an AP.





Wang, et al.                 Standards Track                   [Page 26]

RFC 7798               RTP Payload Format for HEVC            March 2016


   An aggregation unit that is not the first aggregation unit in an AP
   consists of a conditional 8-bit DOND field followed by a 16-bit
   unsigned size information (in network byte order) that indicates the
   size of the NAL unit in bytes (excluding these two octets, but
   including the NAL unit header), followed by the NAL unit itself,
   including its NAL unit header, as shown in Figure 6.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   : DOND (cond)   |          NALU size            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                       NAL unit                                |
   |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 6: The Structure of an Aggregation Unit That Is Not the
   First Aggregation Unit in an AP

   When present, the DOND field plus 1 specifies the difference between
   the decoding order number values of the current aggregated NAL unit
   and the preceding aggregated NAL unit in the same AP.

   If sprop-max-don-diff is greater than 0 for any of the RTP streams,
   the DOND field MUST be present in an aggregation unit that is not the
   first aggregation unit in an AP, and the variable DON for the
   aggregated NAL unit is derived as equal to the DON of the preceding
   aggregated NAL unit in the same AP plus the value of the DOND field
   plus 1 modulo 65536.  Otherwise (sprop-max-don-diff is equal to 0 for
   all the RTP streams), the DOND field MUST NOT be present in an
   aggregation unit that is not the first aggregation unit in an AP, and
   in this case the transmission order and decoding order of NAL units
   carried in the AP are the same as the order the NAL units appear in
   the AP.

   Figure 7 presents an example of an AP that contains two aggregation
   units, labeled as 1 and 2 in the figure, without the DONL and DOND
   fields being present.











Wang, et al.                 Standards Track                   [Page 27]

RFC 7798               RTP Payload Format for HEVC            March 2016


    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          RTP Header                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   PayloadHdr (Type=48)        |         NALU 1 Size           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          NALU 1 HDR           |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+         NALU 1 Data           |
   |                   . . .                                       |
   |                                                               |
   +               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  . . .        | NALU 2 Size                   | NALU 2 HDR    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | NALU 2 HDR    |                                               |
   +-+-+-+-+-+-+-+-+              NALU 2 Data                      |
   |                   . . .                                       |
   |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               :...OPTIONAL RTP padding        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 7: An Example of an AP Packet Containing Two Aggregation
   Units without the DONL and DOND Fields




























Wang, et al.                 Standards Track                   [Page 28]

RFC 7798               RTP Payload Format for HEVC            March 2016


   Figure 8 presents an example of an AP that contains two aggregation
   units, labeled as 1 and 2 in the figure, with the DONL and DOND
   fields being present.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          RTP Header                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   PayloadHdr (Type=48)        |        NALU 1 DONL            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          NALU 1 Size          |            NALU 1 HDR         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                 NALU 1 Data   . . .                           |
   |                                                               |
   +     . . .     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               |  NALU 2 DOND  |          NALU 2 Size          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          NALU 2 HDR           |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+          NALU 2 Data          |
   |                                                               |
   |        . . .                  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               :...OPTIONAL RTP padding        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 8: An Example of an AP Containing Two Aggregation Units
   with the DONL and DOND Fields

4.4.3.  Fragmentation Units

   Fragmentation Units (FUs) are introduced to enable fragmenting a
   single NAL unit into multiple RTP packets, possibly without
   cooperation or knowledge of the HEVC encoder.  A fragment of a NAL
   unit consists of an integer number of consecutive octets of that NAL
   unit.  Fragments of the same NAL unit MUST be sent in consecutive
   order with ascending RTP sequence numbers (with no other RTP packets
   within the same RTP stream being sent between the first and last
   fragment).

   When a NAL unit is fragmented and conveyed within FUs, it is referred
   to as a fragmented NAL unit.  APs MUST NOT be fragmented.  FUs MUST
   NOT be nested; i.e., an FU must not contain a subset of another FU.

   The RTP timestamp of an RTP packet carrying an FU is set to the NALU-
   time of the fragmented NAL unit.





Wang, et al.                 Standards Track                   [Page 29]

RFC 7798               RTP Payload Format for HEVC            March 2016


   An FU consists of a payload header (denoted as PayloadHdr), an FU
   header of one octet, a conditional 16-bit DONL field (in network byte
   order), and an FU payload, as shown in Figure 9.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    PayloadHdr (Type=49)       |   FU header   | DONL (cond)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
   | DONL (cond)   |                                               |
   |-+-+-+-+-+-+-+-+                                               |
   |                         FU payload                            |
   |                                                               |
   |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               :...OPTIONAL RTP padding        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 9: The Structure of an FU

   The fields in the payload header are set as follows.  The Type field
   MUST be equal to 49.  The fields F, LayerId, and TID MUST be equal to
   the fields F, LayerId, and TID, respectively, of the fragmented NAL
   unit.

   The FU header consists of an S bit, an E bit, and a 6-bit FuType
   field, as shown in Figure 10.

   +---------------+
   |0|1|2|3|4|5|6|7|
   +-+-+-+-+-+-+-+-+
   |S|E|  FuType   |
   +---------------+

   Figure 10: The Structure of FU Header

   The semantics of the FU header fields are as follows:

   S: 1 bit
      When set to 1, the S bit indicates the start of a fragmented NAL
      unit, i.e., the first byte of the FU payload is also the first
      byte of the payload of the fragmented NAL unit.  When the FU
      payload is not the start of the fragmented NAL unit payload, the S
      bit MUST be set to 0.








Wang, et al.                 Standards Track                   [Page 30]

RFC 7798               RTP Payload Format for HEVC            March 2016


   E: 1 bit
      When set to 1, the E bit indicates the end of a fragmented NAL
      unit, i.e., the last byte of the payload is also the last byte of
      the fragmented NAL unit.  When the FU payload is not the last
      fragment of a fragmented NAL unit, the E bit MUST be set to 0.

   FuType: 6 bits
      The field FuType MUST be equal to the field Type of the fragmented
      NAL unit.

   The DONL field, when present, specifies the value of the 16 least
   significant bits of the decoding order number of the fragmented NAL
   unit.

   If sprop-max-don-diff is greater than 0 for any of the RTP streams,
   and the S bit is equal to 1, the DONL field MUST be present in the
   FU, and the variable DON for the fragmented NAL unit is derived as
   equal to the value of the DONL field.  Otherwise (sprop-max-don-diff
   is equal to 0 for all the RTP streams, or the S bit is equal to 0),
   the DONL field MUST NOT be present in the FU.

   A non-fragmented NAL unit MUST NOT be transmitted in one FU; i.e.,
   the Start bit and End bit must not both be set to 1 in the same FU
   header.

   The FU payload consists of fragments of the payload of the fragmented
   NAL unit so that if the FU payloads of consecutive FUs, starting with
   an FU with the S bit equal to 1 and ending with an FU with the E bit
   equal to 1, are sequentially concatenated, the payload of the
   fragmented NAL unit can be reconstructed.  The NAL unit header of the
   fragmented NAL unit is not included as such in the FU payload, but
   rather the information of the NAL unit header of the fragmented NAL
   unit is conveyed in F, LayerId, and TID fields of the FU payload
   headers of the FUs and the FuType field of the FU header of the FUs.
   An FU payload MUST NOT be empty.

   If an FU is lost, the receiver SHOULD discard all following
   fragmentation units in transmission order corresponding to the same
   fragmented NAL unit, unless the decoder in the receiver is known to
   be prepared to gracefully handle incomplete NAL units.

   A receiver in an endpoint or in a MANE MAY aggregate the first n-1
   fragments of a NAL unit to an (incomplete) NAL unit, even if fragment
   n of that NAL unit is not received.  In this case, the
   forbidden_zero_bit of the NAL unit MUST be set to 1 to indicate a
   syntax violation.





Wang, et al.                 Standards Track                   [Page 31]

RFC 7798               RTP Payload Format for HEVC            March 2016


4.4.4.  PACI Packets

   This section specifies the PACI packet structure.  The basic payload
   header specified in this memo is intentionally limited to the 16 bits
   of the NAL unit header so to keep the packetization overhead to a
   minimum.  However, cases have been identified where it is advisable
   to include control information in an easily accessible position in
   the packet header, despite the additional overhead.  One such control
   information is the TSCI as specified in Section 4.5.  PACI packets
   carry this and future, similar structures.

   The PACI packet structure is based on a payload header extension
   mechanism that is generic and extensible to carry payload header
   extensions.  In this section, the focus lies on the use within this
   specification.  Section 4.4.4.2 provides guidance for the
   specification designers in how to employ the extension mechanism in
   future specifications.

   A PACI packet consists of a payload header (denoted as PayloadHdr),
   for which the structure follows what is described in Section 4.2.
   The payload header is followed by the fields A, cType, PHSsize,
   F[0..2], and Y.

   Figure 11 shows a PACI packet in compliance with this memo, i.e.,
   without any extensions.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    PayloadHdr (Type=50)       |A|   cType   | PHSsize |F0..2|Y|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Payload Header Extension Structure (PHES)              |
   |=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=|
   |                                                               |
   |                  PACI payload: NAL unit                       |
   |                   . . .                                       |
   |                                                               |
   |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               :...OPTIONAL RTP padding        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 11: The Structure of a PACI









Wang, et al.                 Standards Track                   [Page 32]

RFC 7798               RTP Payload Format for HEVC            March 2016


   The fields in the payload header are set as follows.  The F bit MUST
   be equal to 0.  The Type field MUST be equal to 50.  The value of
   LayerId MUST be a copy of the LayerId field of the PACI payload NAL
   unit or NAL-unit-like structure.  The value of TID MUST be a copy of
   the TID field of the PACI payload NAL unit or NAL-unit-like
   structure.

   The semantics of other fields are as follows:

   A: 1 bit
      Copy of the F bit of the PACI payload NAL unit or NAL-unit-like
      structure.

   cType: 6 bits
      Copy of the Type field of the PACI payload NAL unit or NAL-unit-
      like structure.

   PHSsize: 5 bits
      Indicates the length of the PHES field.  The value is limited to
      be less than or equal to 32 octets, to simplify encoder design for
      MTU size matching.

   F0:
      This field equal to 1 specifies the presence of a temporal
      scalability support extension in the PHES.

   F1, F2:
      MUST be 0, available for future extensions, see Section 4.4.4.2.
      Receivers compliant with this version of the HEVC payload format
      MUST ignore F1=1 and/or F2=1, and also ignore any information in
      the PHES indicated as present by F1=1 and/or F2=1.

         Informative note: The receiver can do that by first decoding
         information associated with F0=1, and then skipping over any
         remaining bytes of the PHES based on the value of PHSsize.

   Y: 1 bit
      MUST be 0, available for future extensions, see Section 4.4.4.2.
      Receivers compliant with this version of the HEVC payload format
      MUST ignore Y=1, and also ignore any information in the PHES
      indicated as present by Y.

   PHES: variable number of octets
      A variable number of octets as indicated by the value of PHSsize.

   PACI Payload:
      The single NAL unit packet or NAL-unit-like structure (such as: FU
      or AP) to be carried, not including the first two octets.



Wang, et al.                 Standards Track                   [Page 33]

RFC 7798               RTP Payload Format for HEVC            March 2016


         Informative note: The first two octets of the NAL unit or NAL-
         unit-like structure carried in the PACI payload are not
         included in the PACI payload.  Rather, the respective values
         are copied in locations of the PayloadHdr of the RTP packet.
         This design offers two advantages: first, the overall structure
         of the payload header is preserved, i.e., there is no special
         case of payload header structure that needs to be implemented
         for PACI.  Second, no additional overhead is introduced.

      A PACI payload MAY be a single NAL unit, an FU, or an AP.  PACIs
      MUST NOT be fragmented or aggregated.  The following subsection
      documents the reasons for these design choices.

4.4.4.1.  Reasons for the PACI Rules (Informative)

   A PACI cannot be fragmented.  If a PACI could be fragmented, and a
   fragment other than the first fragment got lost, access to the
   information in the PACI would not be possible.  Therefore, a PACI
   must not be fragmented.  In other words, an FU must not carry
   (fragments of) a PACI.

   A PACI cannot be aggregated.  Aggregation of PACIs is inadvisable
   from a compression viewpoint, as, in many cases, several to be
   aggregated NAL units would share identical PACI fields and values
   which would be carried redundantly for no reason.  Most, if not all,
   of the practical effects of PACI aggregation can be achieved by
   aggregating NAL units and bundling them with a PACI (see below).
   Therefore, a PACI must not be aggregated.  In other words, an AP must
   not contain a PACI.

   The payload of a PACI can be a fragment.  Both middleboxes and
   sending systems with inflexible (often hardware-based) encoders
   occasionally find themselves in situations where a PACI and its
   headers, combined, are larger than the MTU size.  In such a scenario,
   the middlebox or sender can fragment the NAL unit and encapsulate the
   fragment in a PACI.  Doing so preserves the payload header extension
   information for all fragments, allowing downstream middleboxes and
   the receiver to take advantage of that information.  Therefore, a
   sender may place a fragment into a PACI, and a receiver must be able
   to handle such a PACI.

   The payload of a PACI can be an aggregation NAL unit.  HEVC
   bitstreams can contain unevenly sized and/or small (when compared to
   the MTU size) NAL units.  In order to efficiently packetize such
   small NAL units, APs were introduced.  The benefits of APs are
   independent from the need for a payload header extension.  Therefore,
   a sender may place an AP into a PACI, and a receiver must be able to
   handle such a PACI.



Wang, et al.                 Standards Track                   [Page 34]

RFC 7798               RTP Payload Format for HEVC            March 2016


4.4.4.2.  PACI Extensions (Informative)

   This section includes recommendations for future specification
   designers on how to extent the PACI syntax to accommodate future
   extensions.  Obviously, designers are free to specify whatever
   appears to be appropriate to them at the time of their design.
   However, a lot of thought has been invested into the extension
   mechanism described below, and we suggest that deviations from it
   warrant a good explanation.

   This memo defines only a single payload header extension (TSCI,
   described in Section 4.5); therefore, only the F0 bit carries
   semantics.  F1 and F2 are already named (and not just marked as
   reserved, as a typical video spec designer would do).  They are
   intended to signal two additional extensions.  The Y bit allows one
   to, recursively, add further F and Y bits to extend the mechanism
   beyond three possible payload header extensions.  It is suggested to
   define a new packet type (using a different value for Type) when
   assigning the F1, F2, or Y bits different semantics than what is
   suggested below.

   When a Y bit is set, an 8-bit flag-extension is inserted after the Y
   bit.  A flag-extension consists of 7 flags F[n..n+6], and another Y
   bit.

   The basic PACI header already includes F0, F1, and F2.  Therefore,
   the Fx bits in the first flag-extensions are numbered F3, F4, ...,
   F9; the F bits in the second flag-extension are numbered F10, F11,
   ..., F16, and so forth.  As a result, at least three Fx bits are
   always in the PACI, but the number of Fx bits (and associated types
   of extensions) can be increased by setting the next Y bit and adding
   an octet of flag-extensions, carrying seven flags and another Y bit.
   The size of this list of flags is subject to the limits specified in
   Section 4.4.4 (32 octets for all flag-extensions and the PHES
   information combined).

   Each of the F bits can indicate either the presence or the absence of
   certain information in the Payload Header Extension Structure (PHES).

   When a spec developer devises a new syntax that takes advantage of
   the PACI extension mechanism, he/she must follow the constraints
   listed below; otherwise, the extension mechanism may break.

      1) The fields added for a particular Fx bit MUST be fixed in
         length and not depend on what other Fx bits are set (no parsing
         dependency).

      2) The Fx bits must be assigned in order.



Wang, et al.                 Standards Track                   [Page 35]

RFC 7798               RTP Payload Format for HEVC            March 2016


      3) An implementation that supports the n-th Fn bit for any value
         of n must understand the syntax (though not necessarily the
         semantics) of the fields Fk (with k < n), so as to be able to
         either use those bits when present, or at least be able to skip
         over them.

4.5.  Temporal Scalability Control Information

   This section describes the single payload header extension defined in
   this specification, known as TSCI.  If, in the future, additional
   payload header extensions become necessary, they could be specified
   in this section of an updated version of this document, or in their
   own documents.

   When F0 is set to 1 in a PACI, this specifies that the PHES field
   includes the TSCI fields TL0PICIDX, IrapPicID, S, and E as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    PayloadHdr (Type=50)       |A|   cType   | PHSsize |F0..2|Y|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TL0PICIDX   |   IrapPicID   |S|E|    RES    |               |
   |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
   |                           ....                                |
   |               PACI payload: NAL unit                          |
   |                                                               |
   |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               :...OPTIONAL RTP padding        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 12: The Structure of a PACI with a PHES Containing a TSCI

   TL0PICIDX (8 bits)
      When present, the TL0PICIDX field MUST be set to equal to
      temporal_sub_layer_zero_idx as specified in Section D.3.22 of
      [HEVC] for the access unit containing the NAL unit in the PACI.

   IrapPicID (8 bits)
      When present, the IrapPicID field MUST be set to equal to
      irap_pic_id as specified in Section D.3.22 of [HEVC] for the
      access unit containing the NAL unit in the PACI.









Wang, et al.                 Standards Track                   [Page 36]

RFC 7798               RTP Payload Format for HEVC            March 2016


   S (1 bit)
      The S bit MUST be set to 1 if any of the following conditions is
      true and MUST be set to 0 otherwise:

      o  The NAL unit in the payload of the PACI is the first VCL NAL
         unit, in decoding order, of a picture.

      o  The NAL unit in the payload of the PACI is an AP, and the NAL
         unit in the first contained aggregation unit is the first VCL
         NAL unit, in decoding order, of a picture.

      o  The NAL unit in the payload of the PACI is an FU with its S bit
         equal to 1 and the FU payload containing a fragment of the
         first VCL NAL unit, in decoding order, of a picture.

   E (1 bit)
      The E bit MUST be set to 1 if any of the following conditions is
      true and MUST be set to 0 otherwise:

      o  The NAL unit in the payload of the PACI is the last VCL NAL
         unit, in decoding order, of a picture.

      o  The NAL unit in the payload of the PACI is an AP and the NAL
         unit in the last contained aggregation unit is the last VCL NAL
         unit, in decoding order, of a picture.

      o  The NAL unit in the payload of the PACI is an FU with its E bit
         equal to 1 and the FU payload containing a fragment of the last
         VCL NAL unit, in decoding order, of a picture.

   RES (6 bits)
      MUST be equal to 0.  Reserved for future extensions.

   The value of PHSsize MUST be set to 3.  Receivers MUST allow other
   values of the fields F0, F1, F2, Y, and PHSsize, and MUST ignore any
   additional fields, when present, than specified above in the PHES.

4.6.  Decoding Order Number

   For each NAL unit, the variable AbsDon is derived, representing the
   decoding order number that is indicative of the NAL unit decoding
   order.

   Let NAL unit n be the n-th NAL unit in transmission order within an
   RTP stream.






Wang, et al.                 Standards Track                   [Page 37]

RFC 7798               RTP Payload Format for HEVC            March 2016


   If sprop-max-don-diff is equal to 0 for all the RTP streams carrying
   the HEVC bitstream, AbsDon[n], the value of AbsDon for NAL unit n, is
   derived as equal to n.

   Otherwise (sprop-max-don-diff is greater than 0 for any of the RTP
   streams), AbsDon[n] is derived as follows, where DON[n] is the value
   of the variable DON for NAL unit n:

   o  If n is equal to 0 (i.e., NAL unit n is the very first NAL unit in
      transmission order), AbsDon[0] is set equal to DON[0].

   o  Otherwise (n is greater than 0), the following applies for
      derivation of AbsDon[n]:

      If DON[n] == DON[n-1],
          AbsDon[n] = AbsDon[n-1]

      If (DON[n] > DON[n-1] and DON[n] - DON[n-1] < 32768),
          AbsDon[n] = AbsDon[n-1] + DON[n] - DON[n-1]

      If (DON[n] < DON[n-1] and DON[n-1] - DON[n] >= 32768),
          AbsDon[n] = AbsDon[n-1] + 65536 - DON[n-1] + DON[n]

      If (DON[n] > DON[n-1] and DON[n] - DON[n-1] >= 32768),
          AbsDon[n] = AbsDon[n-1] - (DON[n-1] + 65536 -
          DON[n])

      If (DON[n] < DON[n-1] and DON[n-1] - DON[n] < 32768),
          AbsDon[n] = AbsDon[n-1] - (DON[n-1] - DON[n])

   For any two NAL units m and n, the following applies:

   o  AbsDon[n] greater than AbsDon[m] indicates that NAL unit n follows
      NAL unit m in NAL unit decoding order.

   o  When AbsDon[n] is equal to AbsDon[m], the NAL unit decoding order
      of the two NAL units can be in either order.

   o  AbsDon[n] less than AbsDon[m] indicates that NAL unit n precedes
      NAL unit m in decoding order.

         Informative note: When two consecutive NAL units in the NAL
         unit decoding order have different values of AbsDon, the
         absolute difference between the two AbsDon values may be
         greater than or equal to 1.






Wang, et al.                 Standards Track                   [Page 38]

RFC 7798               RTP Payload Format for HEVC            March 2016


         Informative note: There are multiple reasons to allow for the
         absolute difference of the values of AbsDon for two consecutive
         NAL units in the NAL unit decoding order to be greater than
         one.  An increment by one is not required, as at the time of
         associating values of AbsDon to NAL units, it may not be known
         whether all NAL units are to be delivered to the receiver.  For
         example, a gateway may not forward VCL NAL units of higher sub-
         layers or some SEI NAL units when there is congestion in the
         network.  In another example, the first intra-coded picture of
         a pre-encoded clip is transmitted in advance to ensure that it
         is readily available in the receiver, and when transmitting the
         first intra-coded picture, the originator does not exactly know
         how many NAL units will be encoded before the first intra-coded
         picture of the pre-encoded clip follows in decoding order.
         Thus, the values of AbsDon for the NAL units of the first
         intra-coded picture of the pre-encoded clip have to be
         estimated when they are transmitted, and gaps in values of
         AbsDon may occur.  Another example is MRST or MRMT with sprop-
         max-don-diff greater than 0, where the AbsDon values must
         indicate cross-layer decoding order for NAL units conveyed in
         all the RTP streams.

5.  Packetization Rules

   The following packetization rules apply:

   o  If sprop-max-don-diff is greater than 0 for any of the RTP
      streams, the transmission order of NAL units carried in the RTP
      stream MAY be different than the NAL unit decoding order and the
      NAL unit output order.  Otherwise (sprop-max-don-diff is equal to
      0 for all the RTP streams), the transmission order of NAL units
      carried in the RTP stream MUST be the same as the NAL unit
      decoding order and, when tx-mode is equal to "MRST" or "MRMT",
      MUST also be the same as the NAL unit output order.

   o  A NAL unit of a small size SHOULD be encapsulated in an
      aggregation packet together with one or more other NAL units in
      order to avoid the unnecessary packetization overhead for small
      NAL units.  For example, non-VCL NAL units such as access unit
      delimiters, parameter sets, or SEI NAL units are typically small
      and can often be aggregated with VCL NAL units without violating
      MTU size constraints.

   o  Each non-VCL NAL unit SHOULD, when possible from an MTU size match
      viewpoint, be encapsulated in an aggregation packet together with
      its associated VCL NAL unit, as typically a non-VCL NAL unit would
      be meaningless without the associated VCL NAL unit being
      available.



Wang, et al.                 Standards Track                   [Page 39]

RFC 7798               RTP Payload Format for HEVC            March 2016


   o  For carrying exactly one NAL unit in an RTP packet, a single NAL
      unit packet MUST be used.

6.  De-packetization Process

   The general concept behind de-packetization is to get the NAL units
   out of the RTP packets in an RTP stream and all RTP streams the RTP
   stream depends on, if any, and pass them to the decoder in the NAL
   unit decoding order.

   The de-packetization process is implementation dependent.  Therefore,
   the following description should be seen as an example of a suitable
   implementation.  Other schemes may be used as well, as long as the
   output for the same input is the same as the process described below.
   The output is the same when the set of output NAL units and their
   order are both identical.  Optimizations relative to the described
   algorithms are possible.

   All normal RTP mechanisms related to buffer management apply.  In
   particular, duplicated or outdated RTP packets (as indicated by the
   RTP sequences number and the RTP timestamp) are removed.  To
   determine the exact time for decoding, factors such as a possible
   intentional delay to allow for proper inter-stream synchronization
   must be factored in.

   NAL units with NAL unit type values in the range of 0 to 47,
   inclusive, may be passed to the decoder.  NAL-unit-like structures
   with NAL unit type values in the range of 48 to 63, inclusive, MUST
   NOT be passed to the decoder.

   The receiver includes a receiver buffer, which is used to compensate
   for transmission delay jitter within individual RTP streams and
   across RTP streams, to reorder NAL units from transmission order to
   the NAL unit decoding order, and to recover the NAL unit decoding
   order in MRST or MRMT, when applicable.  In this section, the
   receiver operation is described under the assumption that there is no
   transmission delay jitter within an RTP stream and across RTP
   streams.  To make a difference from a practical receiver buffer that
   is also used for compensation of transmission delay jitter, the
   receiver buffer is hereafter called the de-packetization buffer in
   this section.  Receivers should also prepare for transmission delay
   jitter; that is, either reserve separate buffers for transmission
   delay jitter buffering and de-packetization buffering or use a
   receiver buffer for both transmission delay jitter and de-
   packetization.  Moreover, receivers should take transmission delay
   jitter into account in the buffering operation, e.g., by additional
   initial buffering before starting of decoding and playback.




Wang, et al.                 Standards Track                   [Page 40]

RFC 7798               RTP Payload Format for HEVC            March 2016


   When sprop-max-don-diff is equal to 0 for all the received RTP
   streams, the de-packetization buffer size is zero bytes, and the
   process described in the remainder of this paragraph applies.  When
   there is only one RTP stream received, the NAL units carried in the
   single RTP stream are directly passed to the decoder in their
   transmission order, which is identical to their decoding order.  When
   there is more than one RTP stream received, the NAL units carried in
   the multiple RTP streams are passed to the decoder in their NTP
   timestamp order.  When there are several NAL units of different RTP
   streams with the same NTP timestamp, the order to pass them to the
   decoder is their dependency order, where NAL units of a dependee RTP
   stream are passed to the decoder prior to the NAL units of the
   dependent RTP stream.  When there are several NAL units of the same
   RTP stream with the same NTP timestamp, the order to pass them to the
   decoder is their transmission order.

      Informative note: The mapping between RTP and NTP timestamps is
      conveyed in RTCP SR packets.  In addition, the mechanisms for
      faster media timestamp synchronization discussed in [RFC6051] may
      be used to speed up the acquisition of the RTP-to-wall-clock
      mapping.

   When sprop-max-don-diff is greater than 0 for any the received RTP
   streams, the process described in the remainder of this section
   applies.

   There are two buffering states in the receiver: initial buffering and
   buffering while playing.  Initial buffering starts when the reception
   is initialized.  After initial buffering, decoding and playback are
   started, and the buffering-while-playing mode is used.

   Regardless of the buffering state, the receiver stores incoming NAL
   units, in reception order, into the de-packetization buffer.  NAL
   units carried in RTP packets are stored in the de-packetization
   buffer individually, and the value of AbsDon is calculated and stored
   for each NAL unit.  When MRST or MRMT is in use, NAL units of all RTP
   streams of a bitstream are stored in the same de-packetization
   buffer.  When NAL units carried in any two RTP streams are available
   to be placed into the de-packetization buffer, those NAL units
   carried in the RTP stream that is lower in the dependency tree are
   placed into the buffer first.  For example, if RTP stream A depends
   on RTP stream B, then NAL units carried in RTP stream B are placed
   into the buffer first.








Wang, et al.                 Standards Track                   [Page 41]

RFC 7798               RTP Payload Format for HEVC            March 2016


   Initial buffering lasts until condition A (the difference between the
   greatest and smallest AbsDon values of the NAL units in the de-
   packetization buffer is greater than or equal to the value of sprop-
   max-don-diff of the highest RTP stream) or condition B (the number of
   NAL units in the de-packetization buffer is greater than the value of
   sprop-depack-buf-nalus) is true.

   After initial buffering, whenever condition A or condition B is true,
   the following operation is repeatedly applied until both condition A
   and condition B become false:

      o  The NAL unit in the de-packetization buffer with the smallest
         value of AbsDon is removed from the de-packetization buffer and
         passed to the decoder.

   When no more NAL units are flowing into the de-packetization buffer,
   all NAL units remaining in the de-packetization buffer are removed
   from the buffer and passed to the decoder in the order of increasing
   AbsDon values.

7.  Payload Format Parameters

   This section specifies the parameters that MAY be used to select
   optional features of the payload format and certain features or
   properties of the bitstream or the RTP stream.  The parameters are
   specified here as part of the media type registration for the HEVC
   codec.  A mapping of the parameters into the Session Description
   Protocol (SDP) [RFC4566] is also provided for applications that use
   SDP.  Equivalent parameters could be defined elsewhere for use with
   control protocols that do not use SDP.

7.1.  Media Type Registration

   The media subtype for the HEVC codec is allocated from the IETF tree.

   The receiver MUST ignore any unrecognized parameter.

   Type name:     video

   Subtype name:  H265

   Required parameters: none

   OPTIONAL parameters:

      profile-space, tier-flag, profile-id, profile-compatibility-
      indicator, interop-constraints, and level-id:




Wang, et al.                 Standards Track                   [Page 42]

RFC 7798               RTP Payload Format for HEVC            March 2016


         These parameters indicate the profile, tier, default level, and
         some constraints of the bitstream carried by the RTP stream and
         all RTP streams the RTP stream depends on, or a specific set of
         the profile, tier, default level, and some constraints the
         receiver supports.

         The profile and some constraints are indicated collectively by
         profile-space, profile-id, profile-compatibility-indicator, and
         interop-constraints.  The profile specifies the subset of
         coding tools that may have been used to generate the bitstream
         or that the receiver supports.

            Informative note: There are 32 values of profile-id, and
            there are 32 flags in profile-compatibility-indicator, each
            flag corresponding to one value of profile-id.  According to
            HEVC version 1 in [HEVC], when more than one of the 32 flags
            is set for a bitstream, the bitstream would comply with all
            the profiles corresponding to the set flags.  However, in a
            draft of HEVC version 2 in [HEVCv2], Subclause A.3.5, 19
            Format Range Extensions profiles have been specified, all
            using the same value of profile-id (4), differentiated by
            some of the 48 bits in interop-constraints; this (rather
            unexpected way of profile signaling) means that one of the
            32 flags may correspond to multiple profiles.  To be able to
            support whatever HEVC extension profile that might be
            specified and indicated using profile-space, profile-id,
            profile-compatibility-indicator, and interop-constraints in
            the future, it would be safe to require symmetric use of
            these parameters in SDP offer/answer unless recv-sub-layer-
            id is included in the SDP answer for choosing one of the
            sub-layers offered.

         The tier is indicated by tier-flag.  The default level is
         indicated by level-id.  The tier and the default level specify
         the limits on values of syntax elements or arithmetic
         combinations of values of syntax elements that are followed
         when generating the bitstream or that the receiver supports.

         A set of profile-space, tier-flag, profile-id, profile-
         compatibility-indicator, interop-constraints, and level-id
         parameters ptlA is said to be consistent with another set of
         these parameters ptlB if any decoder that conforms to the
         profile, tier, level, and constraints indicated by ptlB can
         decode any bitstream that conforms to the profile, tier, level,
         and constraints indicated by ptlA.






Wang, et al.                 Standards Track                   [Page 43]

RFC 7798               RTP Payload Format for HEVC            March 2016


         In SDP offer/answer, when the SDP answer does not include the
         recv-sub-layer-id parameter that is less than the sprop-sub-
         layer-id parameter in the SDP offer, the following applies:

            o  The profile-space, tier-flag, profile-id, profile-
               compatibility-indicator, and interop-constraints
               parameters MUST be used symmetrically, i.e., the value of
               each of these parameters in the offer MUST be the same as
               that in the answer, either explicitly signaled or
               implicitly inferred.

            o  The level-id parameter is changeable as long as the
               highest level indicated by the answer is either equal to
               or lower than that in the offer.  Note that the highest
               level is indicated by level-id and max-recv-level-id
               together.

         In SDP offer/answer, when the SDP answer does include the recv-
         sub-layer-id parameter that is less than the sprop-sub-layer-id
         parameter in the SDP offer, the set of profile-space, tier-
         flag, profile-id, profile-compatibility-indicator, interop-
         constraints, and level-id parameters included in the answer
         MUST be consistent with that for the chosen sub-layer
         representation as indicated in the SDP offer, with the
         exception that the level-id parameter in the SDP answer is
         changeable as long as the highest level indicated by the answer
         is either lower than or equal to that in the offer.

         More specifications of these parameters, including how they
         relate to the values of the profile, tier, and level syntax
         elements specified in [HEVC] are provided below.

      profile-space, profile-id:

         The value of profile-space MUST be in the range of 0 to 3,
         inclusive.  The value of profile-id MUST be in the range of 0
         to 31, inclusive.

         When profile-space is not present, a value of 0 MUST be
         inferred.  When profile-id is not present, a value of 1 (i.e.,
         the Main profile) MUST be inferred.

         When used to indicate properties of a bitstream, profile-space
         and profile-id are derived from the profile, tier, and level
         syntax elements in SPS or VPS NAL units as follows, where
         general_profile_space, general_profile_idc,
         sub_layer_profile_space[j], and sub_layer_profile_idc[j] are
         specified in [HEVC]:



Wang, et al.                 Standards Track                   [Page 44]

RFC 7798               RTP Payload Format for HEVC            March 2016


            If the RTP stream is the highest RTP stream, the following
            applies:

            o profile-space = general_profile_space
            o profile-id = general_profile_idc

            Otherwise (the RTP stream is a dependee RTP stream), the
            following applies, with j being the value of the sprop-sub-
            layer-id parameter:

            o profile-space = sub_layer_profile_space[j]
            o profile-id = sub_layer_profile_idc[j]

      tier-flag, level-id:

         The value of tier-flag MUST be in the range of 0 to 1,
         inclusive.  The value of level-id MUST be in the range of 0 to
         255, inclusive.

         If the tier-flag and level-id parameters are used to indicate
         properties of a bitstream, they indicate the tier and the
         highest level the bitstream complies with.

         If the tier-flag and level-id parameters are used for
         capability exchange, the following applies.  If max-recv-level-
         id is not present, the default level defined by level-id
         indicates the highest level the codec wishes to support.
         Otherwise, max-recv-level-id indicates the highest level the
         codec supports for receiving.  For either receiving or sending,
         all levels that are lower than the highest level supported MUST
         also be supported.

         If no tier-flag is present, a value of 0 MUST be inferred; if
         no level-id is present, a value of 93 (i.e., level 3.1) MUST be
         inferred.

         When used to indicate properties of a bitstream, the tier-flag
         and level-id parameters are derived from the profile, tier, and
         level syntax elements in SPS or VPS NAL units as follows, where
         general_tier_flag, general_level_idc, sub_layer_tier_flag[j],
         and sub_layer_level_idc[j] are specified in [HEVC]:

            If the RTP stream is the highest RTP stream, the following
            applies:

            o tier-flag = general_tier_flag
            o level-id = general_level_idc




Wang, et al.                 Standards Track                   [Page 45]

RFC 7798               RTP Payload Format for HEVC            March 2016


            Otherwise (the RTP stream is a dependee RTP stream), the
            following applies, with j being the value of the sprop-sub-
            layer-id parameter:

            o tier-flag = sub_layer_tier_flag[j]
            o level-id = sub_layer_level_idc[j]

      interop-constraints:

         A base16 [RFC4648] (hexadecimal) representation of six bytes of
         data, consisting of progressive_source_flag,
         interlaced_source_flag, non_packed_constraint_flag,
         frame_only_constraint_flag, and reserved_zero_44bits.

         If the interop-constraints parameter is not present, the
         following MUST be inferred:

            o progressive_source_flag = 1
            o interlaced_source_flag = 0
            o non_packed_constraint_flag = 1
            o frame_only_constraint_flag = 1
            o reserved_zero_44bits = 0

         When the interop-constraints parameter is used to indicate
         properties of a bitstream, the following applies, where
         general_progressive_source_flag,
         general_interlaced_source_flag,
         general_non_packed_constraint_flag,
         general_non_packed_constraint_flag,
         general_frame_only_constraint_flag,
         general_reserved_zero_44bits,
         sub_layer_progressive_source_flag[j],
         sub_layer_interlaced_source_flag[j],
         sub_layer_non_packed_constraint_flag[j],
         sub_layer_frame_only_constraint_flag[j], and
         sub_layer_reserved_zero_44bits[j] are specified in [HEVC]:

            If the RTP stream is the highest RTP stream, the following
            applies:

            o progressive_source_flag = general_progressive_source_flag

            o interlaced_source_flag = general_interlaced_source_flag

            o non_packed_constraint_flag =
                 general_non_packed_constraint_flag





Wang, et al.                 Standards Track                   [Page 46]

RFC 7798               RTP Payload Format for HEVC            March 2016


            o frame_only_constraint_flag =
                 general_frame_only_constraint_flag

            o reserved_zero_44bits = general_reserved_zero_44bits

            Otherwise (the RTP stream is a dependee RTP stream), the
            following applies, with j being the value of the sprop-sub-
            layer-id parameter:

            o progressive_source_flag =
                 sub_layer_progressive_source_flag[j]

            o interlaced_source_flag =
                 sub_layer_interlaced_source_flag[j]

            o non_packed_constraint_flag =
                 sub_layer_non_packed_constraint_flag[j]

            o frame_only_constraint_flag =
                 sub_layer_frame_only_constraint_flag[j]

            o reserved_zero_44bits = sub_layer_reserved_zero_44bits[j]

            Using interop-constraints for capability exchange results in
            a requirement on any bitstream to be compliant with the
            interop-constraints.

      profile-compatibility-indicator:

         A base16 [RFC4648] representation of four bytes of data.

         When profile-compatibility-indicator is used to indicate
         properties of a bitstream, the following applies, where
         general_profile_compatibility_flag[j] and
         sub_layer_profile_compatibility_flag[i][j] are specified in
         [HEVC]:

            The profile-compatibility-indicator in this case indicates
            additional profiles to the profile defined by profile-space,
            profile-id, and interop-constraints the bitstream conforms
            to.  A decoder that conforms to any of all the profiles the
            bitstream conforms to would be capable of decoding the
            bitstream.  These additional profiles are defined by
            profile-space, each set bit of profile-compatibility-
            indicator, and interop-constraints.






Wang, et al.                 Standards Track                   [Page 47]

RFC 7798               RTP Payload Format for HEVC            March 2016


            If the RTP stream is the highest RTP stream, the following
            applies for each value of j in the range of 0 to 31,
            inclusive:

            o bit j of profile-compatibility-indicator =
                 general_profile_compatibility_flag[j]

            Otherwise (the RTP stream is a dependee RTP stream), the
            following applies for i equal to sprop-sub-layer-id and for
            each value of j in the range of 0 to 31, inclusive:

            o bit j of profile-compatibility-indicator =
                 sub_layer_profile_compatibility_flag[i][j]

         Using profile-compatibility-indicator for capability exchange
         results in a requirement on any bitstream to be compliant with
         the profile-compatibility-indicator.  This is intended to
         handle cases where any future HEVC profile is defined as an
         intersection of two or more profiles.

         If this parameter is not present, this parameter defaults to
         the following: bit j, with j equal to profile-id, of profile-
         compatibility-indicator is inferred to be equal to 1, and all
         other bits are inferred to be equal to 0.

      sprop-sub-layer-id:

         This parameter MAY be used to indicate the highest allowed
         value of TID in the bitstream.  When not present, the value of
         sprop-sub-layer-id is inferred to be equal to 6.

         The value of sprop-sub-layer-id MUST be in the range of 0 to 6,
         inclusive.

      recv-sub-layer-id:

         This parameter MAY be used to signal a receiver's choice of the
         offered or declared sub-layer representations in the sprop-vps.
         The value of recv-sub-layer-id indicates the TID of the highest
         sub-layer of the bitstream that a receiver supports.  When not
         present, the value of recv-sub-layer-id is inferred to be equal
         to the value of the sprop-sub-layer-id parameter in the SDP
         offer.

         The value of recv-sub-layer-id MUST be in the range of 0 to 6,
         inclusive.





Wang, et al.                 Standards Track                   [Page 48]

RFC 7798               RTP Payload Format for HEVC            March 2016


      max-recv-level-id:

         This parameter MAY be used to indicate the highest level a
         receiver supports.  The highest level the receiver supports is
         equal to the value of max-recv-level-id divided by 30.

         The value of max-recv-level-id MUST be in the range of 0 to
         255, inclusive.

         When max-recv-level-id is not present, the value is inferred to
         be equal to level-id.

         max-recv-level-id MUST NOT be present when the highest level
         the receiver supports is not higher than the default level.

      tx-mode:

         This parameter indicates whether the transmission mode is SRST,
         MRST, or MRMT.

         The value of tx-mode MUST be equal to "SRST", "MRST" or "MRMT".
         When not present, the value of tx-mode is inferred to be equal
         to "SRST".

         If the value is equal to "MRST", MRST MUST be in use.
         Otherwise, if the value is equal to "MRMT", MRMT MUST be in
         use.  Otherwise (the value is equal to "SRST"), SRST MUST be in
         use.

         The value of tx-mode MUST be equal to "MRST" for all RTP
         streams in an MRST.

         The value of tx-mode MUST be equal to "MRMT" for all RTP
         streams in an MRMT.

      sprop-vps:

         This parameter MAY be used to convey any video parameter set
         NAL unit of the bitstream for out-of-band transmission of video
         parameter sets.  The parameter MAY also be used for capability
         exchange and to indicate sub-stream characteristics (i.e.,
         properties of sub-layer representations as defined in [HEVC]).
         The value of the parameter is a comma-separated (',') list of
         base64 [RFC4648] representations of the video parameter set NAL
         units as specified in Section 7.3.2.1 of [HEVC].






Wang, et al.                 Standards Track                   [Page 49]

RFC 7798               RTP Payload Format for HEVC            March 2016


         The sprop-vps parameter MAY contain one or more than one video
         parameter set NAL unit. However, all other video parameter sets
         contained in the sprop-vps parameter MUST be consistent with
         the first video parameter set in the sprop-vps parameter.  A
         video parameter set vpsB is said to be consistent with another
         video parameter set vpsA if any decoder that conforms to the
         profile, tier, level, and constraints indicated by the 12 bytes
         of data starting from the syntax element general_profile_space
         to the syntax element general_level_idc, inclusive, in the
         first profile_tier_level( ) syntax structure in vpsA can decode
         any bitstream that conforms to the profile, tier, level, and
         constraints indicated by the 12 bytes of data starting from the
         syntax element general_profile_space to the syntax element
         general_level_idc, inclusive, in the first profile_tier_level(
         ) syntax structure in vpsB.

      sprop-sps:

         This parameter MAY be used to convey sequence parameter set NAL
         units of the bitstream for out-of-band transmission of sequence
         parameter sets.  The value of the parameter is a comma-
         separated (',') list of base64 [RFC4648] representations of the
         sequence parameter set NAL units as specified in Section
         7.3.2.2 of [HEVC].

      sprop-pps:

         This parameter MAY be used to convey picture parameter set NAL
         units of the bitstream for out-of-band transmission of picture
         parameter sets.  The value of the parameter is a comma-
         separated (',') list of base64 [RFC4648] representations of the
         picture parameter set NAL units as specified in Section 7.3.2.3
         of [HEVC].

      sprop-sei:

         This parameter MAY be used to convey one or more SEI messages
         that describe bitstream characteristics.  When present, a
         decoder can rely on the bitstream characteristics that are
         described in the SEI messages for the entire duration of the
         session, independently from the persistence scopes of the SEI
         messages as specified in [HEVC].

         The value of the parameter is a comma-separated (',') list of
         base64 [RFC4648] representations of SEI NAL units as specified
         in Section 7.3.2.4 of [HEVC].





Wang, et al.                 Standards Track                   [Page 50]

RFC 7798               RTP Payload Format for HEVC            March 2016


            Informative note: Intentionally, no list of applicable or
            inapplicable SEI messages is specified here.  Conveying
            certain SEI messages in sprop-sei may be sensible in some
            application scenarios and meaningless in others.  However, a
            few examples are described below:

               1) In an environment where the bitstream was created from
                  film-based source material, and no splicing is going
                  to occur during the lifetime of the session, the film
                  grain characteristics SEI message or the tone mapping
                  information SEI message are likely meaningful, and
                  sending them in sprop-sei rather than in the bitstream
                  at each entry point may help with saving bits and
                  allows one to configure the renderer only once,
                  avoiding unwanted artifacts.

               2) The structure of pictures information SEI message in
                  sprop-sei can be used to inform a decoder of
                  information on the NAL unit types, picture-order count
                  values, and prediction dependencies of a sequence of
                  pictures.  Having such knowledge can be helpful for
                  error recovery.

               3) Examples for SEI messages that would be meaningless to
                  be conveyed in sprop-sei include the decoded picture
                  hash SEI message (it is close to impossible that all
                  decoded pictures have the same hashtag), the display
                  orientation SEI message when the device is a handheld
                  device (as the display orientation may change when the
                  handheld device is turned around), or the filler
                  payload SEI message (as there is no point in just
                  having more bits in SDP).

      max-lsr, max-lps, max-cpb, max-dpb, max-br, max-tr, max-tc:

         These parameters MAY be used to signal the capabilities of a
         receiver implementation.  These parameters MUST NOT be used for
         any other purpose.  The highest level (specified by max-recv-
         level-id) MUST be the highest that the receiver is fully
         capable of supporting.  max-lsr, max-lps, max-cpb, max-dpb,
         max-br, max-tr, and max-tc MAY be used to indicate capabilities
         of the receiver that extend the required capabilities of the
         highest level, as specified below.

         When more than one parameter from the set (max-lsr, max-lps,
         max-cpb, max-dpb, max-br, max-tr, max-tc) is present, the
         receiver MUST support all signaled capabilities simultaneously.
         For example, if both max-lsr and max-br are present, the



Wang, et al.                 Standards Track                   [Page 51]

RFC 7798               RTP Payload Format for HEVC            March 2016


         highest level with the extension of both the picture rate and
         bitrate is supported.  That is, the receiver is able to decode
         bitstreams in which the luma sample rate is up to max-lsr
         (inclusive), the bitrate is up to max-br (inclusive), the coded
         picture buffer size is derived as specified in the semantics of
         the max-br parameter below, and the other properties comply
         with the highest level specified by max-recv-level-id.

            Informative note: When the OPTIONAL media type parameters
            are used to signal the properties of a bitstream, and max-
            lsr, max-lps, max-cpb, max-dpb, max-br, max-tr, and max-tc
            are not present, the values of profile-space, tier-flag,
            profile-id, profile-compatibility-indicator, interop-
            constraints, and level-id must always be such that the
            bitstream complies fully with the specified profile, tier,
            and level.

      max-lsr:

         The value of max-lsr is an integer indicating the maximum
         processing rate in units of luma samples per second.  The max-
         lsr parameter signals that the receiver is capable of decoding
         video at a higher rate than is required by the highest level.

         When max-lsr is signaled, the receiver MUST be able to decode
         bitstreams that conform to the highest level, with the
         exception that the MaxLumaSR value in Table A-2 of [HEVC] for
         the highest level is replaced with the value of max-lsr.
         Senders MAY use this knowledge to send pictures of a given size
         at a higher picture rate than is indicated in the highest
         level.

         When not present, the value of max-lsr is inferred to be equal
         to the value of MaxLumaSR given in Table A-2 of [HEVC] for the
         highest level.

         The value of max-lsr MUST be in the range of MaxLumaSR to 16 *
         MaxLumaSR, inclusive, where MaxLumaSR is given in Table A-2 of
         [HEVC] for the highest level.

      max-lps:

         The value of max-lps is an integer indicating the maximum
         picture size in units of luma samples.  The max-lps parameter
         signals that the receiver is capable of decoding larger picture
         sizes than are required by the highest level.  When max-lps is
         signaled, the receiver MUST be able to decode bitstreams that
         conform to the highest level, with the exception that the



Wang, et al.                 Standards Track                   [Page 52]

RFC 7798               RTP Payload Format for HEVC            March 2016


         MaxLumaPS value in Table A-1 of [HEVC] for the highest level is
         replaced with the value of max-lps.  Senders MAY use this
         knowledge to send larger pictures at a proportionally lower
         picture rate than is indicated in the highest level.

         When not present, the value of max-lps is inferred to be equal
         to the value of MaxLumaPS given in Table A-1 of [HEVC] for the
         highest level.

         The value of max-lps MUST be in the range of MaxLumaPS to 16 *
         MaxLumaPS, inclusive, where MaxLumaPS is given in Table A-1 of
         [HEVC] for the highest level.

      max-cpb:

         The value of max-cpb is an integer indicating the maximum coded
         picture buffer size in units of CpbBrVclFactor bits for the VCL
         HRD parameters and in units of CpbBrNalFactor bits for the NAL
         HRD parameters, where CpbBrVclFactor and CpbBrNalFactor are
         defined in Section A.4 of [HEVC].  The max-cpb parameter
         signals that the receiver has more memory than the minimum
         amount of coded picture buffer memory required by the highest
         level.  When max-cpb is signaled, the receiver MUST be able to
         decode bitstreams that conform to the highest level, with the
         exception that the MaxCPB value in Table A-1 of [HEVC] for the
         highest level is replaced with the value of max-cpb.  Senders
         MAY use this knowledge to construct coded bitstreams with
         greater variation of bitrate than can be achieved with the
         MaxCPB value in Table A-1 of [HEVC].

         When not present, the value of max-cpb is inferred to be equal
         to the value of MaxCPB given in Table A-1 of [HEVC] for the
         highest level.

         The value of max-cpb MUST be in the range of MaxCPB to 16 *
         MaxCPB, inclusive, where MaxLumaCPB is given in Table A-1 of
         [HEVC] for the highest level.

            Informative note: The coded picture buffer is used in the
            hypothetical reference decoder (Annex C of [HEVC]).  The use
            of the hypothetical reference decoder is recommended in HEVC
            encoders to verify that the produced bitstream conforms to
            the standard and to control the output bitrate.  Thus, the
            coded picture buffer is conceptually independent of any
            other potential buffers in the receiver, including de-
            packetization and de-jitter buffers.  The coded picture
            buffer need not be implemented in decoders as specified in
            Annex C of [HEVC], but rather standard-compliant decoders



Wang, et al.                 Standards Track                   [Page 53]

RFC 7798               RTP Payload Format for HEVC            March 2016


            can have any buffering arrangements provided that they can
            decode standard-compliant bitstreams.  Thus, in practice,
            the input buffer for a video decoder can be integrated with
            de-packetization and de-jitter buffers of the receiver.

      max-dpb:

         The value of max-dpb is an integer indicating the maximum
         decoded picture buffer size in units decoded pictures at the
         MaxLumaPS for the highest level, i.e., the number of decoded
         pictures at the maximum picture size defined by the highest
         level.  The value of max-dpb MUST be in the range of 1 to 16,
         respectively.  The max-dpb parameter signals that the receiver
         has more memory than the minimum amount of decoded picture
         buffer memory required by default, which is MaxDpbPicBuf as
         defined in [HEVC] (equal to 6).  When max-dpb is signaled, the
         receiver MUST be able to decode bitstreams that conform to the
         highest level, with the exception that the MaxDpbPicBuff value
         defined in [HEVC] as 6 is replaced with the value of max-dpb.
         Consequently, a receiver that signals max-dpb MUST be capable
         of storing the following number of decoded pictures
         (MaxDpbSize) in its decoded picture buffer:

           if( PicSizeInSamplesY <= ( MaxLumaPS >> 2 ) )
              MaxDpbSize = Min( 4 * max-dpb, 16 )
           else if ( PicSizeInSamplesY <= ( MaxLumaPS >> 1 ) )
              MaxDpbSize = Min( 2 * max-dpb, 16 )
           else if ( PicSizeInSamplesY <= ( ( 3 * MaxLumaPS ) >> 2
         ) )
              MaxDpbSize = Min( (4 * max-dpb) / 3, 16 )
           else
              MaxDpbSize = max-dpb

         Wherein MaxLumaPS given in Table A-1 of [HEVC] for the highest
         level and PicSizeInSamplesY is the current size of each decoded
         picture in units of luma samples as defined in [HEVC].

         The value of max-dpb MUST be greater than or equal to the value
         of MaxDpbPicBuf (i.e., 6) as defined in [HEVC].  Senders MAY
         use this knowledge to construct coded bitstreams with improved
         compression.

         When not present, the value of max-dpb is inferred to be equal
         to the value of MaxDpbPicBuf (i.e., 6) as defined in [HEVC].

            Informative note: This parameter was added primarily to
            complement a similar codepoint in the ITU-T Recommendation
            H.245, so as to facilitate signaling gateway designs.  The



Wang, et al.                 Standards Track                   [Page 54]

RFC 7798               RTP Payload Format for HEVC            March 2016


            decoded picture buffer stores reconstructed samples.  There
            is no relationship between the size of the decoded picture
            buffer and the buffers used in RTP, especially de-
            packetization and de-jitter buffers.

      max-br:

         The value of max-br is an integer indicating the maximum video
         bitrate in units of CpbBrVclFactor bits per second for the VCL
         HRD parameters and in units of CpbBrNalFactor bits per second
         for the NAL HRD parameters, where CpbBrVclFactor and
         CpbBrNalFactor are defined in Section A.4 of [HEVC].

         The max-br parameter signals that the video decoder of the
         receiver is capable of decoding video at a higher bitrate than
         is required by the highest level.

         When max-br is signaled, the video codec of the receiver MUST
         be able to decode bitstreams that conform to the highest level,
         with the following exceptions in the limits specified by the
         highest level:

            o  The value of max-br replaces the MaxBR value in Table A-2
               of [HEVC] for the highest level.

            o  When the max-cpb parameter is not present, the result of
               the following formula replaces the value of MaxCPB in
               Table A-1 of [HEVC]:

               (MaxCPB of the highest level) * max-br / (MaxBR of the
               highest level)

         For example, if a receiver signals capability for Main profile
         Level 2 with max-br equal to 2000, this indicates a maximum
         video bitrate of 2000 kbits/sec for VCL HRD parameters, a
         maximum video bitrate of 2200 kbits/sec for NAL HRD parameters,
         and a CPB size of 2000000 bits (2000000 / 1500000 * 1500000).

         Senders MAY use this knowledge to send higher bitrate video as
         allowed in the level definition of Annex A of [HEVC] to achieve
         improved video quality.

         When not present, the value of max-br is inferred to be equal
         to the value of MaxBR given in Table A-2 of [HEVC] for the
         highest level.






Wang, et al.                 Standards Track                   [Page 55]

RFC 7798               RTP Payload Format for HEVC            March 2016


         The value of max-br MUST be in the range of MaxBR to 16 *
         MaxBR, inclusive, where MaxBR is given in Table A-2 of [HEVC]
         for the highest level.

            Informative note: This parameter was added primarily to
            complement a similar codepoint in the ITU-T Recommendation
            H.245, so as to facilitate signaling gateway designs.  The
            assumption that the network is capable of handling such
            bitrates at any given time cannot be made from the value of
            this parameter.  In particular, no conclusion can be drawn
            that the signaled bitrate is possible under congestion
            control constraints.

      max-tr:

         The value of max-tr is an integer indication the maximum number
         of tile rows.  The max-tr parameter signals that the receiver
         is capable of decoding video with a larger number of tile rows
         than the value allowed by the highest level.

         When max-tr is signaled, the receiver MUST be able to decode
         bitstreams that conform to the highest level, with the
         exception that the MaxTileRows value in Table A-1 of [HEVC] for
         the highest level is replaced with the value of max-tr.

         Senders MAY use this knowledge to send pictures utilizing a
         larger number of tile rows than the value allowed by the
         highest level.

         When not present, the value of max-tr is inferred to be equal
         to the value of MaxTileRows given in Table A-1 of [HEVC] for
         the highest level.

         The value of max-tr MUST be in the range of MaxTileRows to 16 *
         MaxTileRows, inclusive, where MaxTileRows is given in Table A-1
         of [HEVC] for the highest level.

      max-tc:

         The value of max-tc is an integer indication the maximum number
         of tile columns.  The max-tc parameter signals that the
         receiver is capable of decoding video with a larger number of
         tile columns than the value allowed by the highest level.

         When max-tc is signaled, the receiver MUST be able to decode
         bitstreams that conform to the highest level, with the
         exception that the MaxTileCols value in Table A-1 of [HEVC] for
         the highest level is replaced with the value of max-tc.



Wang, et al.                 Standards Track                   [Page 56]

RFC 7798               RTP Payload Format for HEVC            March 2016


         Senders MAY use this knowledge to send pictures utilizing a
         larger number of tile columns than the value allowed by the
         highest level.

         When not present, the value of max-tc is inferred to be equal
         to the value of MaxTileCols given in Table A-1 of [HEVC] for
         the highest level.

         The value of max-tc MUST be in the range of MaxTileCols to 16 *
         MaxTileCols, inclusive, where MaxTileCols is given in Table A-1
         of [HEVC] for the highest level.

      max-fps:

         The value of max-fps is an integer indicating the maximum
         picture rate in units of pictures per 100 seconds that can be
         effectively processed by the receiver.  The max-fps parameter
         MAY be used to signal that the receiver has a constraint in
         that it is not capable of processing video effectively at the
         full picture rate that is implied by the highest level and,
         when present, one or more of the parameters max-lsr, max-lps,
         and max-br.

         The value of max-fps is not necessarily the picture rate at
         which the maximum picture size can be sent, it constitutes a
         constraint on maximum picture rate for all resolutions.

            Informative note: The max-fps parameter is semantically
            different from max-lsr, max-lps, max-cpb, max-dpb, max-br,
            max-tr, and max-tc in that max-fps is used to signal a
            constraint, lowering the maximum picture rate from what is
            implied by other parameters.

         The encoder MUST use a picture rate equal to or less than this
         value.  In cases where the max-fps parameter is absent, the
         encoder is free to choose any picture rate according to the
         highest level and any signaled optional parameters.

         The value of max-fps MUST be smaller than or equal to the full
         picture rate that is implied by the highest level and, when
         present, one or more of the parameters max-lsr, max-lps, and
         max-br.









Wang, et al.                 Standards Track                   [Page 57]

RFC 7798               RTP Payload Format for HEVC            March 2016


      sprop-max-don-diff:

         If tx-mode is equal to "SRST" and there is no NAL unit naluA
         that is followed in transmission order by any NAL unit
         preceding naluA in decoding order (i.e., the transmission order
         of the NAL units is the same as the decoding order), the value
         of this parameter MUST be equal to 0.

         Otherwise, if tx-mode is equal to "MRST" or "MRMT", the
         decoding order of the NAL units of all the RTP streams is the
         same as the NAL unit transmission order and the NAL unit output
         order, the value of this parameter MUST be equal to either 0 or
         1.

         Otherwise, if tx-mode is equal to "MRST" or "MRMT" and the
         decoding order of the NAL units of all the RTP streams is the
         same as the NAL unit transmission order but not the same as the
         NAL unit output order, the value of this parameter MUST be
         equal to 1.

         Otherwise, this parameter specifies the maximum absolute
         difference between the decoding order number (i.e., AbsDon)
         values of any two NAL units naluA and naluB, where naluA
         follows naluB in decoding order and precedes naluB in
         transmission order.

         The value of sprop-max-don-diff MUST be an integer in the range
         of 0 to 32767, inclusive.

         When not present, the value of sprop-max-don-diff is inferred
         to be equal to 0.

      sprop-depack-buf-nalus:

         This parameter specifies the maximum number of NAL units that
         precede a NAL unit in transmission order and follow the NAL
         unit in decoding order.

         The value of sprop-depack-buf-nalus MUST be an integer in the
         range of 0 to 32767, inclusive.

         When not present, the value of sprop-depack-buf-nalus is
         inferred to be equal to 0.

         When sprop-max-don-diff is present and greater than 0, this
         parameter MUST be present and the value MUST be greater than 0.





Wang, et al.                 Standards Track                   [Page 58]

RFC 7798               RTP Payload Format for HEVC            March 2016


      sprop-depack-buf-bytes:

         This parameter signals the required size of the de-
         packetization buffer in units of bytes.  The value of the
         parameter MUST be greater than or equal to the maximum buffer
         occupancy (in units of bytes) of the de-packetization buffer as
         specified in Section 6.

         The value of sprop-depack-buf-bytes MUST be an integer in the
         range of 0 to 4294967295, inclusive.

         When sprop-max-don-diff is present and greater than 0, this
         parameter MUST be present and the value MUST be greater than 0.
         When not present, the value of sprop-depack-buf-bytes is
         inferred to be equal to 0.

            Informative note: The value of sprop-depack-buf-bytes
            indicates the required size of the de-packetization buffer
            only.  When network jitter can occur, an appropriately sized
            jitter buffer has to be available as well.

      depack-buf-cap:

         This parameter signals the capabilities of a receiver
         implementation and indicates the amount of de-packetization
         buffer space in units of bytes that the receiver has available
         for reconstructing the NAL unit decoding order from NAL units
         carried in one or more RTP streams.  A receiver is able to
         handle any RTP stream, and all RTP streams the RTP stream
         depends on, when present, for which the value of the sprop-
         depack-buf-bytes parameter is smaller than or equal to this
         parameter.

         When not present, the value of depack-buf-cap is inferred to be
         equal to 4294967295.  The value of depack-buf-cap MUST be an
         integer in the range of 1 to 4294967295, inclusive.

            Informative note: depack-buf-cap indicates the maximum
            possible size of the de-packetization buffer of the receiver
            only, without allowing for network jitter.











Wang, et al.                 Standards Track                   [Page 59]

RFC 7798               RTP Payload Format for HEVC            March 2016


      sprop-segmentation-id:

         This parameter MAY be used to signal the segmentation tools
         present in the bitstream and that can be used for
         parallelization.  The value of sprop-segmentation-id MUST be an
         integer in the range of 0 to 3, inclusive.  When not present,
         the value of sprop-segmentation-id is inferred to be equal to
         0.

         When sprop-segmentation-id is equal to 0, no information about
         the segmentation tools is provided.  When sprop-segmentation-id
         is equal to 1, it indicates that slices are present in the
         bitstream.  When sprop-segmentation-id is equal to 2, it
         indicates that tiles are present in the bitstream.  When sprop-
         segmentation-id is equal to 3, it indicates that WPP is used in
         the bitstream.

      sprop-spatial-segmentation-idc:

         A base16 [RFC4648] representation of the syntax element
         min_spatial_segmentation_idc as specified in [HEVC].  This
         parameter MAY be used to describe parallelization capabilities
         of the bitstream.

      dec-parallel-cap:

         This parameter MAY be used to indicate the decoder's additional
         decoding capabilities given the presence of tools enabling
         parallel decoding, such as slices, tiles, and WPP, in the
         bitstream.  The decoding capability of the decoder may vary
         with the setting of the parallel decoding tools present in the
         bitstream, e.g., the size of the tiles that are present in a
         bitstream.  Therefore, multiple capability points may be
         provided, each indicating the minimum required decoding
         capability that is associated with a parallelism requirement,
         which is a requirement on the bitstream that enables parallel
         decoding.

         Each capability point is defined as a combination of 1) a
         parallelism requirement, 2) a profile (determined by profile-
         space and profile-id), 3) a highest level, and 4) a maximum
         processing rate, a maximum picture size, and a maximum video
         bitrate that may be equal to or greater than that determined by
         the highest level.  The parameter's syntax in ABNF [RFC5234] is
         as follows:






Wang, et al.                 Standards Track                   [Page 60]

RFC 7798               RTP Payload Format for HEVC            March 2016


         dec-parallel-cap = "dec-parallel-cap={" cap-point *(","
                            cap-point) "}"

         cap-point = ("w" / "t") ":" spatial-seg-idc 1*(";"
                      cap-parameter)

         spatial-seg-idc = 1*4DIGIT ; (1-4095)

         cap-parameter = tier-flag / level-id / max-lsr
                         / max-lps / max-br

         tier-flag = "tier-flag" EQ ("0" / "1")

         level-id  = "level-id" EQ 1*3DIGIT ; (0-255)

         max-lsr   = "max-lsr" EQ  1*20DIGIT ; (0-
         18,446,744,073,709,551,615)

         max-lps   = "max-lps" EQ 1*10DIGIT ; (0-4,294,967,295)

         max-br    = "max-br"  EQ 1*20DIGIT ; (0-
         18,446,744,073,709,551,615)

         EQ = "="

         The set of capability points expressed by the dec-parallel-cap
         parameter is enclosed in a pair of curly braces ("{}").  Each
         set of two consecutive capability points is separated by a
         comma (',').  Within each capability point, each set of two
         consecutive parameters, and, when present, their values, is
         separated by a semicolon (';').

         The profile of all capability points is determined by profile-
         space and profile-id, which are outside the dec-parallel-cap
         parameter.

         Each capability point starts with an indication of the
         parallelism requirement, which consists of a parallel tool
         type, which may be equal to 'w' or 't', and a decimal value of
         the spatial-seg-idc parameter.  When the type is 'w', the
         capability point is valid only for H.265 bitstreams with WPP in
         use, i.e., entropy_coding_sync_enabled_flag equal to 1.  When
         the type is 't', the capability point is valid only for H.265
         bitstreams with WPP not in use (i.e.,
         entropy_coding_sync_enabled_flag equal to 0).  The capability-
         point is valid only for H.265 bitstreams with
         min_spatial_segmentation_idc equal to or greater than spatial-
         seg-idc.



Wang, et al.                 Standards Track                   [Page 61]

RFC 7798               RTP Payload Format for HEVC            March 2016


         After the parallelism requirement indication, each capability
         point continues with one or more pairs of parameter and value
         in any order for any of the following parameters:

            o tier-flag
            o level-id
            o max-lsr
            o max-lps
            o max-br

         At most, one occurrence of each of the above five parameters is
         allowed within each capability point.

         The values of dec-parallel-cap.tier-flag and dec-parallel-
         cap.level-id for a capability point indicate the highest level
         of the capability point.  The values of dec-parallel-cap.max-
         lsr, dec-parallel-cap.max-lps, and dec-parallel-cap.max-br for
         a capability point indicate the maximum processing rate in
         units of luma samples per second, the maximum picture size in
         units of luma samples, and the maximum video bitrate (in units
         of CpbBrVclFactor bits per second for the VCL HRD parameters
         and in units of CpbBrNalFactor bits per second for the NAL HRD
         parameters where CpbBrVclFactor and CpbBrNalFactor are defined
         in Section A.4 of [HEVC]).

         When not present, the value of dec-parallel-cap.tier-flag is
         inferred to be equal to the value of tier-flag outside the dec-
         parallel-cap parameter.  When not present, the value of dec-
         parallel-cap.level-id is inferred to be equal to the value of
         max-recv-level-id outside the dec-parallel-cap parameter.  When
         not present, the value of dec-parallel-cap.max-lsr, dec-
         parallel-cap.max-lps, or dec-parallel-cap.max-br is inferred to
         be equal to the value of max-lsr, max-lps, or max-br,
         respectively, outside the dec-parallel-cap parameter.

         The general decoding capability, expressed by the set of
         parameters outside of dec-parallel-cap, is defined as the
         capability point that is determined by the following
         combination of parameters: 1) the parallelism requirement
         corresponding to the value of sprop-segmentation-id equal to 0
         for a bitstream, 2) the profile determined by profile-space,
         profile-id, profile-compatibility-indicator, and interop-
         constraints, 3) the tier and the highest level determined by
         tier-flag and max-recv-level-id, and 4) the maximum processing
         rate, the maximum picture size, and the maximum video bitrate
         determined by the highest level.  The general decoding
         capability MUST NOT be included as one of the set of capability
         points in the dec-parallel-cap parameter.



Wang, et al.                 Standards Track                   [Page 62]

RFC 7798               RTP Payload Format for HEVC            March 2016


         For example, the following parameters express the general
         decoding capability of 720p30 (Level 3.1) plus an additional
         decoding capability of 1080p30 (Level 4) given that the
         spatially largest tile or slice used in the bitstream is equal
         to or less than 1/3 of the picture size:

            a=fmtp:98 level-id=93;dec-parallel-cap={t:8;level- id=120}

         For another example, the following parameters express an
         additional decoding capability of 1080p30, using dec-parallel-
         cap.max-lsr and dec-parallel-cap.max-lps, given that WPP is
         used in the bitstream:

            a=fmtp:98 level-id=93;dec-parallel-cap={w:8;
                        max-lsr=62668800;max-lps=2088960}

            Informative note: When min_spatial_segmentation_idc is
            present in a bitstream and WPP is not used, [HEVC] specifies
            that there is no slice or no tile in the bitstream
            containing more than 4 * PicSizeInSamplesY / (
            min_spatial_segmentation_idc + 4 ) luma samples.

      include-dph:

         This parameter is used to indicate the capability and
         preference to utilize or include Decoded Picture Hash (DPH) SEI
         messages (see Section D.3.19 of [HEVC]) in the bitstream. DPH
         SEI messages can be used to detect picture corruption so the
         receiver can request picture repair, see Section 8.  The value
         is a comma-separated list of hash types that is supported or
         requested to be used, each hash type provided as an unsigned
         integer value (0-255), with the hash types listed from most
         preferred to the least preferred.  Example: "include-dph=0,2",
         which indicates the capability for MD5 (most preferred) and
         Checksum (less preferred).  If the parameter is not included or
         the value contains no hash types, then no capability to utilize
         DPH SEI messages is assumed.  Note that DPH SEI messages MAY
         still be included in the bitstream even when there is no
         declaration of capability to use them, as in general SEI
         messages do not affect the normative decoding process and
         decoders are allowed to ignore SEI messages.

   Encoding considerations:

      This type is only defined for transfer via RTP (RFC 3550).






Wang, et al.                 Standards Track                   [Page 63]

RFC 7798               RTP Payload Format for HEVC            March 2016


   Security considerations:

      See Section 9 of RFC 7798.

   Published specification:

      Please refer to RFC 7798 and its Section 12.

   Additional information: None

   File extensions: none

   Macintosh file type code: none

   Object identifier or OID: none

   Person & email address to contact for further information:

      Ye-Kui Wang (yekui.wang@gmail.com)

   Intended usage: COMMON

   Author: See Authors' Addresses section of RFC 7798.

   Change controller:

      IETF Audio/Video Transport Payloads working group delegated from
      the IESG.

7.2.  SDP Parameters

   The receiver MUST ignore any parameter unspecified in this memo.

7.2.1.  Mapping of Payload Type Parameters to SDP

   The media type video/H265 string is mapped to fields in the Session
   Description Protocol (SDP) [RFC4566] as follows:

   o  The media name in the "m=" line of SDP MUST be video.

   o  The encoding name in the "a=rtpmap" line of SDP MUST be H265 (the
      media subtype).

   o  The clock rate in the "a=rtpmap" line MUST be 90000.

   o  The OPTIONAL parameters profile-space, profile-id, tier-flag,
      level-id, interop-constraints, profile-compatibility-indicator,
      sprop-sub-layer-id, recv-sub-layer-id, max-recv-level-id, tx-mode,



Wang, et al.                 Standards Track                   [Page 64]

RFC 7798               RTP Payload Format for HEVC            March 2016


      max-lsr, max-lps, max-cpb, max-dpb, max-br, max-tr, max-tc, max-
      fps, sprop-max-don-diff, sprop-depack-buf-nalus, sprop-depack-buf-
      bytes, depack-buf-cap, sprop-segmentation-id, sprop-spatial-
      segmentation-idc, dec-parallel-cap, and include-dph, when present,
      MUST be included in the "a=fmtp" line of SDP.  This parameter is
      expressed as a media type string, in the form of a semicolon-
      separated list of parameter=value pairs.

   o  The OPTIONAL parameters sprop-vps, sprop-sps, and sprop-pps, when
      present, MUST be included in the "a=fmtp" line of SDP or conveyed
      using the "fmtp" source attribute as specified in Section 6.3 of
      [RFC5576].  For a particular media format (i.e., RTP payload
      type), sprop-vps sprop-sps, or sprop-pps MUST NOT be both included
      in the "a=fmtp" line of SDP and conveyed using the "fmtp" source
      attribute.  When included in the "a=fmtp" line of SDP, these
      parameters are expressed as a media type string, in the form of a
      semicolon-separated list of parameter=value pairs.  When conveyed
      in the "a=fmtp" line of SDP for a particular payload type, the
      parameters sprop-vps, sprop-sps, and sprop-pps MUST be applied to
      each SSRC with the payload type.  When conveyed using the "fmtp"
      source attribute, these parameters are only associated with the
      given source and payload type as parts of the "fmtp" source
      attribute.

         Informative note: Conveyance of sprop-vps, sprop-sps, and
         sprop-pps using the "fmtp" source attribute allows for out-of-
         band transport of parameter sets in topologies like Topo-Video-
         switch-MCU as specified in [RFC7667].

   An example of media representation in SDP is as follows:

      m=video 49170 RTP/AVP 98
      a=rtpmap:98 H265/90000
      a=fmtp:98 profile-id=1;
                sprop-vps=<video parameter sets data>

7.2.2.  Usage with SDP Offer/Answer Model

   When HEVC is offered over RTP using SDP in an offer/answer model
   [RFC3264] for negotiation for unicast usage, the following
   limitations and rules apply:

   o  The parameters identifying a media format configuration for HEVC
      are profile-space, profile-id, tier-flag, level-id, interop-
      constraints, profile-compatibility-indicator, and tx-mode.  These
      media configuration parameters, except level-id, MUST be used
      symmetrically when the answerer does not include recv-sub-layer-id




Wang, et al.                 Standards Track                   [Page 65]

RFC 7798               RTP Payload Format for HEVC            March 2016


      in the answer for the media format (payload type) or the included
      recv-sub-layer-id is equal to sprop-sub-layer-id in the offer.
      The answerer MUST:

      1) maintain all configuration parameters with the values remaining
         the same as in the offer for the media format (payload type),
         with the exception that the value of level-id is changeable as
         long as the highest level indicated by the answer is not higher
         than that indicated by the offer;

      2) include in the answer the recv-sub-layer-id parameter, with a
         value less than the sprop-sub-layer-id parameter in the offer,
         for the media format (payload type), and maintain all
         configuration parameters with the values being the same as
         signaled in the sprop-vps for the chosen sub-layer
         representation, with the exception that the value of level-id
         is changeable as long as the highest level indicated by the
         answer is not higher than the level indicated by the sprop-vps
         in offer for the chosen sub-layer representation; or

      3) remove the media format (payload type) completely (when one or
         more of the parameter values are not supported).

            Informative note: The above requirement for symmetric use
            does not apply for level-id, and does not apply for the
            other bitstream or RTP stream properties and capability
            parameters.

   o  The profile-compatibility-indicator, when offered as sendonly,
      describes bitstream properties.  The answerer MAY accept an RTP
      payload type even if the decoder is not capable of handling the
      profile indicated by the profile-space, profile-id, and interop-
      constraints parameters, but capable of any of the profiles
      indicated by the profile-space, profile-compatibility-indicator,
      and interop-constraints.  However, when the profile-compatibility-
      indicator is used in a recvonly or sendrecv media description, the
      bitstream using this RTP payload type is required to conform to
      all profiles indicated by profile-space, profile-compatibility-
      indicator, and interop-constraints.

   o  To simplify handling and matching of these configurations, the
      same RTP payload type number used in the offer SHOULD also be used
      in the answer, as specified in [RFC3264].

   o  The same RTP payload type number used in the offer for the media
      subtype H265 MUST be used in the answer when the answer includes
      recv-sub-layer-id.  When the answer does not include recv-sub-
      layer-id, the answer MUST NOT contain a payload type number used



Wang, et al.                 Standards Track                   [Page 66]

RFC 7798               RTP Payload Format for HEVC            March 2016


      in the offer for the media subtype H265 unless the configuration
      is exactly the same as in the offer or the configuration in the
      answer only differs from that in the offer with a different value
      of level-id.  The answer MAY contain the recv-sub-layer-id
      parameter if an HEVC bitstream contains multiple operation points
      (using temporal scalability and sub-layers) and sprop-vps is
      included in the offer where information of sub-layers are present
      in the first video parameter set contained in sprop-vps.  If the
      sprop-vps is provided in an offer, an answerer MAY select a
      particular operation point indicated in the first video parameter
      set contained in sprop-vps.  When the answer includes a recv-sub-
      layer-id that is less than a sprop-sub-layer-id in the offer, all
      video parameter sets contained in the sprop-vps parameter in the
      SDP answer and all video parameter sets sent in-band for either
      the offerer-to-answerer direction or the answerer-to-offerer
      direction MUST be consistent with the first video parameter set in
      the sprop-vps parameter of the offer (see the semantics of sprop-
      vps in Section 7.1 of this document on one video parameter set
      being consistent with another video parameter set), and the
      bitstream sent in either direction MUST conform to the profile,
      tier, level, and constraints of the chosen sub-layer
      representation as indicated by the first profile_tier_level( )
      syntax structure in the first video parameter set in the sprop-vps
      parameter of the offer.

         Informative note: When an offerer receives an answer that does
         not include recv-sub-layer-id, it has to compare payload types
         not declared in the offer based on the media type (i.e.,
         video/H265) and the above media configuration parameters with
         any payload types it has already declared.  This will enable it
         to determine whether the configuration in question is new or if
         it is equivalent to configuration already offered, since a
         different payload type number may be used in the answer.  The
         ability to perform operation point selection enables a receiver
         to utilize the temporal scalable nature of an HEVC bitstream.

   o  The parameters sprop-max-don-diff, sprop-depack-buf-nalus, and
      sprop-depack-buf-bytes describe the properties of an RTP stream,
      and all RTP streams the RTP stream depends on, when present, that
      the offerer or the answerer is sending for the media format
      configuration.  This differs from the normal usage of the
      offer/answer parameters: normally such parameters declare the
      properties of the bitstream or RTP stream that the offerer or the
      answerer is able to receive.  When dealing with HEVC, the offerer
      assumes that the answerer will be able to receive media encoded
      using the configuration being offered.





Wang, et al.                 Standards Track                   [Page 67]

RFC 7798               RTP Payload Format for HEVC            March 2016


         Informative note:  The above parameters apply for any RTP
         stream and all RTP streams the RTP stream depends on, when
         present, sent by a declaring entity with the same
         configuration.  In other words, the applicability of the above
         parameters to RTP streams depends on the source endpoint.
         Rather than being bound to the payload type, the values may
         have to be applied to another payload type when being sent, as
         they apply for the configuration.

   o  The capability parameters max-lsr, max-lps, max-cpb, max-dpb, max-
      br, max-tr, and max-tc MAY be used to declare further capabilities
      of the offerer or answerer for receiving.  These parameters MUST
      NOT be present when the direction attribute is sendonly.

   o  The capability parameter max-fps MAY be used to declare lower
      capabilities of the offerer or answerer for receiving.  The
      parameters MUST NOT be present when the direction attribute is
      sendonly.

   o  The capability parameter dec-parallel-cap MAY be used to declare
      additional decoding capabilities of the offerer or answerer for
      receiving.  Upon receiving such a declaration of a receiver, a
      sender MAY send a bitstream to the receiver utilizing those
      capabilities under the assumption that the bitstream fulfills the
      parallelism requirement.  A bitstream that is sent based on
      choosing a capability point with parallel tool type 'w' from dec-
      parallel-cap MUST have entropy_coding_sync_enabled_flag equal to 1
      and min_spatial_segmentation_idc equal to or larger than dec-
      parallel-cap.spatial-seg-idc of the capability point.  A bitstream
      that is sent based on choosing a capability point with parallel
      tool type 't' from dec-parallel-cap MUST have
      entropy_coding_sync_enabled_flag equal to 0 and
      min_spatial_segmentation_idc equal to or larger than dec-parallel-
      cap.spatial-seg-idc of the capability point.

   o  An offerer has to include the size of the de-packetization buffer,
      sprop-depack-buf-bytes, as well as sprop-max-don-diff and sprop-
      depack-buf-nalus, in the offer for an interleaved HEVC bitstream
      or for the MRST or MRMT transmission mode when sprop-max-don-diff
      is greater than 0 for at least one of the RTP streams.  To enable
      the offerer and answerer to inform each other about their
      capabilities for de-packetization buffering in receiving RTP
      streams, both parties are RECOMMENDED to include depack-buf-cap.
      For interleaved RTP streams or in MRST or MRMT, it is also
      RECOMMENDED to consider offering multiple payload types with
      different buffering requirements when the capabilities of the
      receiver are unknown.




Wang, et al.                 Standards Track                   [Page 68]

RFC 7798               RTP Payload Format for HEVC            March 2016


   o  The capability parameter include-dph MAY be used to declare the
      capability to utilize decoded picture hash SEI messages and which
      types of hashes in any HEVC RTP streams received by the offerer or
      answerer.

   o  The sprop-vps, sprop-sps, or sprop-pps, when present (included in
      the "a=fmtp" line of SDP or conveyed using the "fmtp" source
      attribute as specified in Section 6.3 of [RFC5576]), are used for
      out-of-band transport of the parameter sets (VPS, SPS, or PPS,
      respectively).

   o  The answerer MAY use either out-of-band or in-band transport of
      parameter sets for the bitstream it is sending, regardless of
      whether out-of-band parameter sets transport has been used in the
      offerer-to-answerer direction.  Parameter sets included in an
      answer are independent of those parameter sets included in the
      offer, as they are used for decoding two different bitstreams, one
      from the answerer to the offerer and the other in the opposite
      direction.  In case some RTP streams are sent before the SDP
      offer/answer settles down, in-band parameter sets MUST be used for
      those RTP stream parts sent before the SDP offer/answer.

   o  The following rules apply to transport of parameter set in the
      offerer-to-answerer direction.

      +  An offer MAY include sprop-vps, sprop-sps, and/or sprop-pps.
         If none of these parameters is present in the offer, then only
         in-band transport of parameter sets is used.

      +  If the level to use in the offerer-to-answerer direction is
         equal to the default level in the offer, the answerer MUST be
         prepared to use the parameter sets included in sprop-vps,
         sprop-sps, and sprop-pps (either included in the "a=fmtp" line
         of SDP or conveyed using the "fmtp" source attribute) for
         decoding the incoming bitstream, e.g., by passing these
         parameter set NAL units to the video decoder before passing any
         NAL units carried in the RTP streams.  Otherwise, the answerer
         MUST ignore sprop-vps, sprop-sps, and sprop-pps (either
         included in the "a=fmtp" line of SDP or conveyed using the
         "fmtp" source attribute) and the offerer MUST transmit
         parameter sets in-band.

      +  In MRST or MRMT, the answerer MUST be prepared to use the
         parameter sets out-of-band transmitted for the RTP stream and
         all RTP streams the RTP stream depends on, when present, for
         decoding the incoming bitstream, e.g., by passing these
         parameter set NAL units to the video decoder before passing any
         NAL units carried in the RTP streams.



Wang, et al.                 Standards Track                   [Page 69]

RFC 7798               RTP Payload Format for HEVC            March 2016


   o  The following rules apply to transport of parameter set in the
      answerer-to-offerer direction.

      +  An answer MAY include sprop-vps, sprop-sps, and/or sprop-pps.
         If none of these parameters is present in the answer, then only
         in-band transport of parameter sets is used.

      +  The offerer MUST be prepared to use the parameter sets included
         in sprop-vps, sprop-sps, and sprop-pps (either included in the
         "a=fmtp" line of SDP or conveyed using the "fmtp" source
         attribute) for decoding the incoming bitstream, e.g., by
         passing these parameter set NAL units to the video decoder
         before passing any NAL units carried in the RTP streams.

      +  In MRST or MRMT, the offerer MUST be prepared to use the
         parameter sets out-of-band transmitted for the RTP stream and
         all RTP streams the RTP stream depends on, when present, for
         decoding the incoming bitstream, e.g., by passing these
         parameter set NAL units to the video decoder before passing any
         NAL units carried in the RTP streams.

   o  When sprop-vps, sprop-sps, and/or sprop-pps are conveyed using the
      "fmtp" source attribute as specified in Section 6.3 of [RFC5576],
      the receiver of the parameters MUST store the parameter sets
      included in sprop-vps, sprop-sps, and/or sprop-pps and associate
      them with the source given as part of the "fmtp" source attribute.
      Parameter sets associated with one source (given as part of the
      "fmtp" source attribute) MUST only be used to decode NAL units
      conveyed in RTP packets from the same source (given as part of the
      "fmtp" source attribute).  When this mechanism is in use, SSRC
      collision detection and resolution MUST be performed as specified
      in [RFC5576].

   For bitstreams being delivered over multicast, the following rules
   apply:

      o  The media format configuration is identified by profile-space,
         profile-id, tier-flag, level-id, interop-constraints, profile-
         compatibility-indicator, and tx-mode.  These media format
         configuration parameters, including level-id, MUST be used
         symmetrically; that is, the answerer MUST either maintain all
         configuration parameters or remove the media format (payload
         type) completely.  Note that this implies that the level-id for
         offer/answer in multicast is not changeable.







Wang, et al.                 Standards Track                   [Page 70]

RFC 7798               RTP Payload Format for HEVC            March 2016


      o  To simplify the handling and matching of these configurations,
         the same RTP payload type number used in the offer SHOULD also
         be used in the answer, as specified in [RFC3264].  An answer
         MUST NOT contain a payload type number used in the offer unless
         the configuration is the same as in the offer.

      o  Parameter sets received MUST be associated with the originating
         source and MUST only be used in decoding the incoming bitstream
         from the same source.

      o  The rules for other parameters are the same as above for
         unicast as long as the three above rules are obeyed.

   Table 1 lists the interpretation of all the parameters that MUST be
   used for the various combinations of offer, answer, and direction
   attributes.  Note that the two columns wherein the recv-sub-layer-id
   parameter is used only apply to answers, whereas the other columns
   apply to both offers and answers.

   Table 1.  Interpretation of parameters for various combinations of
   offers, answers, direction attributes, with and without recv-sub-
   layer-id.  Columns that do not indicate offer or answer apply to
   both.




























Wang, et al.                 Standards Track                   [Page 71]

RFC 7798               RTP Payload Format for HEVC            March 2016


                                       sendonly --+
         answer: recvonly, recv-sub-layer-id --+  |
           recvonly w/o recv-sub-layer-id --+  |  |
   answer: sendrecv, recv-sub-layer-id --+  |  |  |
     sendrecv w/o recv-sub-layer-id --+  |  |  |  |
                                      |  |  |  |  |
   profile-space                      C  D  C  D  P
   profile-id                         C  D  C  D  P
   tier-flag                          C  D  C  D  P
   level-id                           D  D  D  D  P
   interop-constraints                C  D  C  D  P
   profile-compatibility-indicator    C  D  C  D  P
   tx-mode                            C  C  C  C  P
   max-recv-level-id                  R  R  R  R  -
   sprop-max-don-diff                 P  P  -  -  P
   sprop-depack-buf-nalus             P  P  -  -  P
   sprop-depack-buf-bytes             P  P  -  -  P
   depack-buf-cap                     R  R  R  R  -
   sprop-segmentation-id              P  P  P  P  P
   sprop-spatial-segmentation-idc     P  P  P  P  P
   max-br                             R  R  R  R  -
   max-cpb                            R  R  R  R  -
   max-dpb                            R  R  R  R  -
   max-lsr                            R  R  R  R  -
   max-lps                            R  R  R  R  -
   max-tr                             R  R  R  R  -
   max-tc                             R  R  R  R  -
   max-fps                            R  R  R  R  -
   sprop-vps                          P  P  -  -  P
   sprop-sps                          P  P  -  -  P
   sprop-pps                          P  P  -  -  P
   sprop-sub-layer-id                 P  P  -  -  P
   recv-sub-layer-id                  X  O  X  O  -
   dec-parallel-cap                   R  R  R  R  -
   include-dph                        R  R  R  R  -

   Legend:

    C: configuration for sending and receiving bitstreams
    D: changeable configuration, same as C except possible
       to answer with a different but consistent value (see the
       semantics of the six parameters related to profile, tier,
       and level on these parameters being consistent)
    P: properties of the bitstream to be sent
    R: receiver capabilities
    O: operation point selection
    X: MUST NOT be present
    -: not usable, when present MUST be ignored



Wang, et al.                 Standards Track                   [Page 72]

RFC 7798               RTP Payload Format for HEVC            March 2016


   Parameters used for declaring receiver capabilities are, in general,
   downgradable; i.e., they express the upper limit for a sender's
   possible behavior.  Thus, a sender MAY select to set its encoder
   using only lower/lesser or equal values of these parameters.

   When the answer does not include a recv-sub-layer-id that is less
   than the sprop-sub-layer-id in the offer, parameters declaring a
   configuration point are not changeable, with the exception of the
   level-id parameter for unicast usage, and these parameters express
   values a receiver expects to be used and MUST be used verbatim in the
   answer as in the offer.

   When a sender's capabilities are declared with the configuration
   parameters, these parameters express a configuration that is
   acceptable for the sender to receive bitstreams.  In order to achieve
   high interoperability levels, it is often advisable to offer multiple
   alternative configurations.  It is impossible to offer multiple
   configurations in a single payload type.  Thus, when multiple
   configuration offers are made, each offer requires its own RTP
   payload type associated with the offer.  However, it is possible to
   offer multiple operation points using one configuration in a single
   payload type by including sprop-vps in the offer and recv-sub-layer-
   id in the answer.

   A receiver SHOULD understand all media type parameters, even if it
   only supports a subset of the payload format's functionality.  This
   ensures that a receiver is capable of understanding when an offer to
   receive media can be downgraded to what is supported by the receiver
   of the offer.

   An answerer MAY extend the offer with additional media format
   configurations.  However, to enable their usage, in most cases a
   second offer is required from the offerer to provide the bitstream
   property parameters that the media sender will use.  This also has
   the effect that the offerer has to be able to receive this media
   format configuration, not only to send it.

7.2.3.  Usage in Declarative Session Descriptions

   When HEVC over RTP is offered with SDP in a declarative style, as in
   Real Time Streaming Protocol (RTSP) [RFC2326] or Session Announcement
   Protocol (SAP) [RFC2974], the following considerations are necessary.









Wang, et al.                 Standards Track                   [Page 73]

RFC 7798               RTP Payload Format for HEVC            March 2016


      o  All parameters capable of indicating both bitstream properties
         and receiver capabilities are used to indicate only bitstream
         properties.  For example, in this case, the parameter profile-
         tier-level-id declares the values used by the bitstream, not
         the capabilities for receiving bitstreams.  As a result, the
         following interpretation of the parameters MUST be used:

         + Declaring actual configuration or bitstream properties:
            - profile-space
            - profile-id
            - tier-flag
            - level-id
            - interop-constraints
            - profile-compatibility-indicator
            - tx-mode
            - sprop-vps
            - sprop-sps
            - sprop-pps
            - sprop-max-don-diff
            - sprop-depack-buf-nalus
            - sprop-depack-buf-bytes
            - sprop-segmentation-id
            - sprop-spatial-segmentation-idc

         + Not usable (when present, they MUST be ignored):
            - max-lps
            - max-lsr
            - max-cpb
            - max-dpb
            - max-br
            - max-tr
            - max-tc
            - max-fps
            - max-recv-level-id
            - depack-buf-cap
            - sprop-sub-layer-id
            - dec-parallel-cap
            - include-dph

      o  A receiver of the SDP is required to support all parameters and
         values of the parameters provided; otherwise, the receiver MUST
         reject (RTSP) or not participate in (SAP) the session.  It
         falls on the creator of the session to use values that are
         expected to be supported by the receiving application.







Wang, et al.                 Standards Track                   [Page 74]

RFC 7798               RTP Payload Format for HEVC            March 2016


7.2.4.  Considerations for Parameter Sets

   When out-of-band transport of parameter sets is used, parameter sets
   MAY still be additionally transported in-band unless explicitly
   disallowed by an application, and some of these additional parameter
   sets may update some of the out-of-band transported parameter sets.
   Update of a parameter set refers to the sending of a parameter set of
   the same type using the same parameter set ID but with different
   values for at least one other parameter of the parameter set.

7.2.5.  Dependency Signaling in Multi-Stream Mode

   If MRST or MRMT is used, the rules on signaling media decoding
   dependency in SDP as defined in [RFC5583] apply.  The rules on
   "hierarchical or layered encoding" with multicast in Section 5.7 of
   [RFC4566] do not apply.  This means that the notation for Connection
   Data "c=" SHALL NOT be used with more than one address, i.e., the
   sub-field <number of addresses> in the sub-field <connection-address>
   of the "c=" field, described in [RFC4566], must not be present.  The
   order of session dependency is given from the RTP stream containing
   the lowest temporal sub-layer to the RTP stream containing the
   highest temporal sub-layer.

8.  Use with Feedback Messages

   The following subsections define the use of the Picture Loss
   Indication (PLI), Slice Lost Indication (SLI), Reference Picture
   Selection Indication (RPSI), and Full Intra Request (FIR) feedback
   messages with HEVC.  The PLI, SLI, and RPSI messages are defined in
   [RFC4585], and the FIR message is defined in [RFC5104].

8.1.  Picture Loss Indication (PLI)

   As specified in RFC 4585, Section 6.3.1, the reception of a PLI by a
   media sender indicates "the loss of an undefined amount of coded
   video data belonging to one or more pictures".  Without having any
   specific knowledge of the setup of the bitstream (such as use and
   location of in-band parameter sets, non-IDR decoder refresh points,
   picture structures, and so forth), a reaction to the reception of an
   PLI by an HEVC sender SHOULD be to send an IDR picture and relevant
   parameter sets; potentially with sufficient redundancy so to ensure
   correct reception.  However, sometimes information about the
   bitstream structure is known.  For example, state could have been
   established outside of the mechanisms defined in this document that
   parameter sets are conveyed out of band only, and stay static for the
   duration of the session.  In that case, it is obviously unnecessary
   to send them in-band as a result of the reception of a PLI.  Other




Wang, et al.                 Standards Track                   [Page 75]

RFC 7798               RTP Payload Format for HEVC            March 2016


   examples could be devised based on a priori knowledge of different
   aspects of the bitstream structure.  In all cases, the timing and
   congestion control mechanisms of RFC 4585 MUST be observed.

8.2.  Slice Loss Indication (SLI)

   The SLI described in RFC 4585 can be used to indicate, to a sender,
   the loss of a number of Coded Tree Blocks (CTBs) in a CTB raster scan
   order of a picture.  In the SLI's Feedback Control Indication (FCI)
   field, the subfield "First" MUST be set to the CTB address of the
   first lost CTB.  Note that the CTB address is in CTB-raster-scan
   order of a picture.  For the first CTB of a slice segment, the CTB
   address is the value of slice_segment_address when present, or 0 when
   the value of first_slice_segment_in_pic_flag is equal to 1; both
   syntax elements are in the slice segment header.  The subfield
   "Number" MUST be set to the number of consecutive lost CTBs, again in
   CTB-raster-scan order of a picture.  Note that due to both the
   "First" and "Number" being counted in CTBs in CTB-raster-scan order,
   of a picture, not in tile-scan order (which is the bitstream order of
   CTBs), multiple SLI messages may be needed to report the loss of one
   tile covering multiple CTB rows but less wide than the picture.

   The subfield "PictureID" MUST be set to the 6 least significant bits
   of a binary representation of the value of PicOrderCntVal, as defined
   in [HEVC], of the picture for which the lost CTBs are indicated.
   Note that for IDR pictures the syntax element slice_pic_order_cnt_lsb
   is not present, but then the value is inferred to be equal to 0.

   As described in RFC 4585, an encoder in a media sender can use this
   information to "clean up" the corrupted picture by sending intra
   information, while observing the constraints described in RFC 4585,
   for example, with respect to congestion control.  In many cases,
   error tracking is required to identify the corrupted region in the
   receiver's state (reference pictures) because of error import in
   uncorrupted regions of the picture through motion compensation.
   Reference-picture selection can also be used to "clean up" the
   corrupted picture, which is usually more efficient and less likely to
   generate congestion than sending intra information.

   In contrast to the video codecs contemplated in RFCs 4585 and 5104
   [RFC5104], in HEVC, the "macroblock size" is not fixed to 16x16 luma
   samples, but is variable.  That, however, does not create a
   conceptual difficulty with SLI, because the setting of the CTB size
   is a sequence-level functionality, and using a slice loss indication
   across CVS boundaries is meaningless as there is no prediction across
   sequence boundaries.  However, a proper use of SLI messages is not as
   straightforward as it was with older, fixed-macroblock-sized video




Wang, et al.                 Standards Track                   [Page 76]

RFC 7798               RTP Payload Format for HEVC            March 2016


   codecs, as the state of the sequence parameter set (where the CTB
   size is located) has to be taken into account when interpreting the
   "First" subfield in the FCI.

8.3.  Reference Picture Selection Indication (RPSI)

   Feedback-based reference picture selection has been shown as a
   powerful tool to stop temporal error propagation for improved error
   resilience [Girod99][Wang05].  In one approach, the decoder side
   tracks errors in the decoded pictures and informs the encoder side
   that a particular picture that has been decoded relatively earlier is
   correct and still present in the decoded picture buffer; it requests
   the encoder to use that correct picture-availability information when
   encoding the next picture, so to stop further temporal error
   propagation.  For this approach, the decoder side should use the RPSI
   feedback message.

   Encoders can encode some long-term reference pictures as specified in
   H.264 or HEVC for purposes described in the previous paragraph
   without the need of a huge decoded picture buffer.  As shown in
   [Wang05], with a flexible reference picture management scheme, as in
   H.264 and HEVC, even a decoded picture buffer size of two picture
   storage buffers would work for the approach described in the previous
   paragraph.

   The field "Native RPSI bit string defined per codec" is a base16
   [RFC4648] representation of the 8 bits consisting of the 2 most
   significant bits equal to 0 and 6 bits of nuh_layer_id, as defined in
   [HEVC], followed by the 32 bits representing the value of the
   PicOrderCntVal (in network byte order), as defined in [HEVC], for the
   picture that is indicated by the RPSI feedback message.

   The use of the RPSI feedback message as positive acknowledgement with
   HEVC is deprecated.  In other words, the RPSI feedback message MUST
   only be used as a reference picture selection request, such that it
   can also be used in multicast.

8.4.  Full Intra Request (FIR)

   The purpose of the FIR message is to force an encoder to send an
   independent decoder refresh point as soon as possible (observing, for
   example, the congestion-control-related constraints set out in RFC
   5104).

   Upon reception of a FIR, a sender MUST send an IDR picture.
   Parameter sets MUST also be sent, except when there is a priori
   knowledge that the parameter sets have been correctly established.  A




Wang, et al.                 Standards Track                   [Page 77]

RFC 7798               RTP Payload Format for HEVC            March 2016


   typical example for that is an understanding between sender and
   receiver, established by means outside this document, that parameter
   sets are exclusively sent out-of-band.

9.  Security Considerations

   The scope of this Security Considerations section is limited to the
   payload format itself and to one feature of HEVC that may pose a
   particularly serious security risk if implemented naively.  The
   payload format, in isolation, does not form a complete system.
   Implementers are advised to read and understand relevant security-
   related documents, especially those pertaining to RTP (see the
   Security Considerations section in [RFC3550]), and the security of
   the call-control stack chosen (that may make use of the media type
   registration of this memo).  Implementers should also consider known
   security vulnerabilities of video coding and decoding implementations
   in general and avoid those.

   Within this RTP payload format, and with the exception of the user
   data SEI message as described below, no security threats other than
   those common to RTP payload formats are known.  In other words,
   neither the various media-plane-based mechanisms, nor the signaling
   part of this memo, seems to pose a security risk beyond those common
   to all RTP-based systems.

   RTP packets using the payload format defined in this specification
   are subject to the security considerations discussed in the RTP
   specification [RFC3550], and in any applicable RTP profile such as
   RTP/AVP [RFC3551], RTP/AVPF [RFC4585], RTP/SAVP [RFC3711], or
   RTP/SAVPF [RFC5124].  However, as "Securing the RTP Framework: Why
   RTP Does Not Mandate a Single Media Security Solution" [RFC7202]
   discusses, it is not an RTP payload format's responsibility to
   discuss or mandate what solutions are used to meet the basic security
   goals like confidentiality, integrity and source authenticity for RTP
   in general.  This responsibility lays on anyone using RTP in an
   application.  They can find guidance on available security mechanisms
   and important considerations in "Options for Securing RTP Sessions"
   [RFC7201].  Applications SHOULD use one or more appropriate strong
   security mechanisms.  The rest of this section discusses the security
   impacting properties of the payload format itself.

   Because the data compression used with this payload format is applied
   end-to-end, any encryption needs to be performed after compression.
   A potential denial-of-service threat exists for data encodings using
   compression techniques that have non-uniform receiver-end
   computational load.  The attacker can inject pathological datagrams
   into the bitstream that are complex to decode and that cause the
   receiver to be overloaded.  H.265 is particularly vulnerable to such



Wang, et al.                 Standards Track                   [Page 78]

RFC 7798               RTP Payload Format for HEVC            March 2016


   attacks, as it is extremely simple to generate datagrams containing
   NAL units that affect the decoding process of many future NAL units.
   Therefore, the usage of data origin authentication and data integrity
   protection of at least the RTP packet is RECOMMENDED, for example,
   with SRTP [RFC3711].

   Like [H.264], HEVC includes a user data Supplemental Enhancement
   Information (SEI) message.  This SEI message allows inclusion of an
   arbitrary bitstring into the video bitstream.  Such a bitstring could
   include JavaScript, machine code, and other active content.  HEVC
   leaves the handling of this SEI message to the receiving system.  In
   order to avoid harmful side effects of the user data SEI message,
   decoder implementations cannot naively trust its content.  For
   example, it would be a bad and insecure implementation practice to
   forward any JavaScript a decoder implementation detects to a web
   browser.  The safest way to deal with user data SEI messages is to
   simply discard them, but that can have negative side effects on the
   quality of experience by the user.

   End-to-end security with authentication, integrity, or
   confidentiality protection will prevent a MANE from performing media-
   aware operations other than discarding complete packets.  In the case
   of confidentiality protection, it will even be prevented from
   discarding packets in a media-aware way.  To be allowed to perform
   such operations, a MANE is required to be a trusted entity that is
   included in the security context establishment.

10.  Congestion Control

   Congestion control for RTP SHALL be used in accordance with RTP
   [RFC3550] and with any applicable RTP profile, e.g., AVP [RFC3551].
   If best-effort service is being used, an additional requirement is
   that users of this payload format MUST monitor packet loss to ensure
   that the packet loss rate is within an acceptable range.  Packet loss
   is considered acceptable if a TCP flow across the same network path,
   and experiencing the same network conditions, would achieve an
   average throughput, measured on a reasonable timescale, that is not
   less than all RTP streams combined is achieving.  This condition can
   be satisfied by implementing congestion-control mechanisms to adapt
   the transmission rate, the number of layers subscribed for a layered
   multicast session, or by arranging for a receiver to leave the
   session if the loss rate is unacceptably high.

   The bitrate adaptation necessary for obeying the congestion control
   principle is easily achievable when real-time encoding is used, for
   example, by adequately tuning the quantization parameter.





Wang, et al.                 Standards Track                   [Page 79]

RFC 7798               RTP Payload Format for HEVC            March 2016


   However, when pre-encoded content is being transmitted, bandwidth
   adaptation requires the pre-coded bitstream to be tailored for such
   adaptivity.  The key mechanism available in HEVC is temporal
   scalability.  A media sender can remove NAL units belonging to higher
   temporal sub-layers (i.e., those NAL units with a high value of TID)
   until the sending bitrate drops to an acceptable range.  HEVC
   contains mechanisms that allow the lightweight identification of
   switching points in temporal enhancement layers, as discussed in
   Section 1.1.2 of this memo.  An HEVC media sender can send packets
   belonging to NAL units of temporal enhancement layers starting from
   these switching points to probe for available bandwidth and to
   utilized bandwidth that has been shown to be available.

   Above mechanisms generally work within a defined profile and level
   and, therefore, no renegotiation of the channel is required.  Only
   when non-downgradable parameters (such as profile) are required to be
   changed does it become necessary to terminate and restart the RTP
   stream(s).  This may be accomplished by using different RTP payload
   types.

   MANEs MAY remove certain unusable packets from the RTP stream when
   that RTP stream was damaged due to previous packet losses.  This can
   help reduce the network load in certain special cases.  For example,
   MANES can remove those FUs where the leading FUs belonging to the
   same NAL unit have been lost or those dependent slice segments when
   the leading slice segments belonging to the same slice have been
   lost, because the trailing FUs or dependent slice segments are
   meaningless to most decoders.  MANES can also remove higher temporal
   scalable layers if the outbound transmission (from the MANE's
   viewpoint) experiences congestion.

11.  IANA Considerations

   A new media type, as specified in Section 7.1 of this memo, has been
   registered with IANA.

12.  References

12.1.  Normative References

   [H.264]   ITU-T, "Advanced video coding for generic audiovisual
             services", ITU-T Recommendation H.264, April 2013.

   [HEVC]    ITU-T, "High efficiency video coding", ITU-T Recommendation
             H.265, April 2013.






Wang, et al.                 Standards Track                   [Page 80]

RFC 7798               RTP Payload Format for HEVC            March 2016


   [ISO23008-2]
             ISO/IEC, "Information technology -- High efficiency coding
             and media delivery in heterogeneous environments -- Part 2:
             High efficiency video coding", ISO/IEC 23008-2, 2013.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119,
             DOI 10.17487/RFC2119, March 1997,
             <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
             with Session Description Protocol (SDP)", RFC 3264,
             DOI 10.17487/RFC3264, June 2002,
             <http://www.rfc-editor.org/info/rfc3264>.

   [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
             Jacobson, "RTP: A Transport Protocol for Real-Time
             Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, July
             2003, <http://www.rfc-editor.org/info/rfc3550>.

   [RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
             Video Conferences with Minimal Control", STD 65, RFC 3551,
             DOI 10.17487/RFC3551, July 2003,
             <http://www.rfc-editor.org/info/rfc3551>.

   [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
             Norrman, "The Secure Real-time Transport Protocol (SRTP)",
             RFC 3711, DOI 10.17487/RFC3711, March 2004,
             <http://www.rfc-editor.org/info/rfc3711>.

   [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
             Description Protocol", RFC 4566, DOI 10.17487/RFC4566, July
             2006, <http://www.rfc-editor.org/info/rfc4566>.

   [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
             "Extended RTP Profile for Real-time Transport Control
             Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
             DOI 10.17487/RFC4585, July 2006,
             <http://www.rfc-editor.org/info/rfc4585>.

   [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
             Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
             <http://www.rfc-editor.org/info/rfc4648>.

   [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
             "Codec Control Messages in the RTP Audio-Visual Profile
             with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104,
             February 2008, <http://www.rfc-editor.org/info/rfc5104>.



Wang, et al.                 Standards Track                   [Page 81]

RFC 7798               RTP Payload Format for HEVC            March 2016


   [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for
             Real-time Transport Control Protocol (RTCP)-Based Feedback
             (RTP/SAVPF)", RFC 5124, DOI 10.17487/RFC5124, February
             2008, <http://www.rfc-editor.org/info/rfc5124>.

   [RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for Syntax
             Specifications: ABNF", STD 68, RFC 5234,
             DOI 10.17487/RFC5234, January 2008,
             <http://www.rfc-editor.org/info/rfc5234>.

   [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific Media
             Attributes in the Session Description Protocol (SDP)",
             RFC 5576, DOI 10.17487/RFC5576, June 2009,
             <http://www.rfc-editor.org/info/rfc5576>.

   [RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding
             Dependency in the Session Description Protocol (SDP)",
             RFC 5583, DOI 10.17487/RFC5583, July 2009,
             <http://www.rfc-editor.org/info/rfc5583>.

12.2.  Informative References

   [3GPDASH] 3GPP, "Transparent end-to-end Packet-switched Streaming
             Service (PSS); Progressive Download and Dynamic Adaptive
             Streaming over HTTP (3GP-DASH)", 3GPP TS 26.247 12.1.0,
             December 2013.

   [3GPPFF]  3GPP, "Transparent end-to-end packet switched streaming
             service (PSS); 3GPP file format (3GP)", 3GPP TS 26.244
             12.20, December 2013.

   [CABAC]   Sole, J., Joshi, R., Nguyen, N., Ji, T., Karczewicz, M.,
             Clare, G., Henry, F., and Duenas, A., "Transform
             coefficient coding in HEVC", IEEE Transactions on Circuts
             and Systems for Video Technology, Vol. 22, No. 12,
             pp. 1765-1777, DOI 10.1109/TCSVT.2012.2223055, December
             2012.

   [Girod99] Girod, B. and Faerber, F., "Feedback-based error control
             for mobile video transmission", Proceedings of the IEEE,
             Vol. 87, No. 10, pp. 1707-1723, DOI 10.1109/5.790632,
             October 1999.

   [H.265.1] ITU-T, "Conformance specification for ITU-T H.265 high
             efficiency video coding", ITU-T Recommendation H.265.1,
             October 2014.





Wang, et al.                 Standards Track                   [Page 82]

RFC 7798               RTP Payload Format for HEVC            March 2016


   [HEVCv2]  Flynn, D., Naccari, M., Rosewarne, C., Sharman, K., Sole,
             J., Sullivan, G. J., and T. Suzuki, "High Efficiency Video
             Coding (HEVC) Range Extensions text specification: Draft
             7", JCT-VC document JCTVC-Q1005, 17th JCT-VC meeting,
             Valencia, Spain, March/April 2014.

   [IS014496-12]
             IS0/IEC, "Information technology - Coding of audio-visual
             objects - Part 12: ISO base media file format", IS0/IEC
             14496-12, 2015.

   [IS015444-12]
             IS0/IEC, "Information technology - JPEG 2000 image coding
             system - Part 12: ISO base media file format", IS0/IEC
             15444-12, 2015.

   [JCTVC-J0107]
             Wang, Y.-K., Chen, Y., Joshi, R., and Ramasubramonian, K.,
             "AHG9: On RAP pictures", JCT-VC document JCTVC-L0107, 10th
             JCT-VC meeting, Stockholm, Sweden, July 2012.

   [MPEG2S]  ISO/IEC, "Information technology - Generic coding of moving
             pictures and associated audio information - Part 1:
             Systems", ISO International Standard 13818-1, 2013.

   [MPEGDASH] ISO/IEC, "Information technology - Dynamic adaptive
             streaming over HTTP (DASH) -- Part 1: Media presentation
             description and segment formats", ISO International
             Standard 23009-1, 2012.

   [RFC2326] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time
             Streaming Protocol (RTSP)", RFC 2326, DOI 10.17487/RFC2326,
             April 1998, <http://www.rfc-editor.org/info/rfc2326>.

   [RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session
             Announcement Protocol", RFC 2974, DOI 10.17487/RFC2974,
             October 2000, <http://www.rfc-editor.org/info/rfc2974>.

   [RFC6051] Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP
             Flows", RFC 6051, DOI 10.17487/RFC6051, November 2010,
             <http://www.rfc-editor.org/info/rfc6051>.

   [RFC6184] Wang, Y.-K., Even, R., Kristensen, T., and R. Jesup, "RTP
             Payload Format for H.264 Video", RFC 6184,
             DOI 10.17487/RFC6184, May 2011,
             <http://www.rfc-editor.org/info/rfc6184>.





Wang, et al.                 Standards Track                   [Page 83]

RFC 7798               RTP Payload Format for HEVC            March 2016


   [RFC6190] Wenger, S., Wang, Y.-K., Schierl, T., and A. Eleftheriadis,
             "RTP Payload Format for Scalable Video Coding", RFC 6190,
             DOI 10.17487/RFC6190, May 2011,
             <http://www.rfc-editor.org/info/rfc6190>.

   [RFC7201] Westerlund, M. and C. Perkins, "Options for Securing RTP
             Sessions", RFC 7201, DOI 10.17487/RFC7201, April 2014,
             <http://www.rfc-editor.org/info/rfc7201>.

   [RFC7202] Perkins, C. and M. Westerlund, "Securing the RTP Framework:
             Why RTP Does Not Mandate a Single Media Security Solution",
             RFC 7202, DOI 10.17487/RFC7202, April 2014,
             <http://www.rfc-editor.org/info/rfc7202>.

   [RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and
             B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms for
             Real-Time Transport Protocol (RTP) Sources", RFC 7656,
             DOI 10.17487/RFC7656, November 2015,
             <http://www.rfc-editor.org/info/rfc7656>.

   [RFC7667] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 7667,
             DOI 10.17487/RFC7667, November 2015,
             <http://www.rfc-editor.org/info/rfc7667>.

   [RTP-MULTI-STREAM]
             Lennox, J., Westerlund, M., Wu, Q., and C. Perkins,
             "Sending Multiple Media Streams in a Single RTP Session",
             Work in Progress, draft-ietf-avtcore-rtp-multi-stream-11,
             December 2015.

   [SDP-NEG] Holmberg, C., Alvestrand, H., and C. Jennings, "Negotiating
             Medai Multiplexing Using Session Description Protocol
             (SDP)", Work in Progress,
             draft-ietf-mmusic-sdp-bundle-negotiation-25, January 2016.

   [Wang05]  Wang, Y.-K., Zhu, C., and Li, H., "Error resilient video
             coding using flexible reference fames", Visual
             Communications and Image Processing 2005 (VCIP 2005),
             Beijing, China, July 2005.












Wang, et al.                 Standards Track                   [Page 84]

RFC 7798               RTP Payload Format for HEVC            March 2016


Acknowledgements

   Muhammed Coban and Marta Karczewicz are thanked for discussions on
   the specification of the use with feedback messages and other aspects
   in this memo.  Jonathan Lennox and Jill Boyce are thanked for their
   contributions to the PACI design included in this memo.  Rickard
   Sjoberg, Arild Fuldseth, Bo Burman, Magnus Westerlund, and Tom
   Kristensen are thanked for their contributions to signaling related
   to parallel processing.  Magnus Westerlund, Jonathan Lennox, Bernard
   Aboba, Jonatan Samuelsson, Roni Even, Rickard Sjoberg, Sachin
   Deshpande, Woo Johnman, Mo Zanaty, Ross Finlayson, Danny Hong, Bo
   Burman, Ben Campbell, Brian Carpenter, Qin Wu, Stephen Farrell, and
   Min Wang made valuable review comments that led to improvements.






































Wang, et al.                 Standards Track                   [Page 85]

RFC 7798               RTP Payload Format for HEVC            March 2016


Authors' Addresses

   Ye-Kui Wang
   Qualcomm Incorporated
   5775 Morehouse Drive
   San Diego, CA 92121
   United States
   Phone: +1-858-651-8345
   Email: yekui.wang@gmail.com

   Yago Sanchez
   Fraunhofer HHI
   Einsteinufer 37
   D-10587 Berlin
   Germany
   Phone: +49 30 31002-663
   Email: yago.sanchez@hhi.fraunhofer.de

   Thomas Schierl
   Fraunhofer HHI
   Einsteinufer 37
   D-10587 Berlin
   Germany
   Phone: +49-30-31002-227
   Email: thomas.schierl@hhi.fraunhofer.de

   Stephan Wenger
   Vidyo, Inc.
   433 Hackensack Ave., 7th floor
   Hackensack, NJ 07601
   United States
   Phone: +1-415-713-5473
   Email: stewe@stewe.org

   Miska M. Hannuksela
   Nokia Corporation
   P.O. Box 1000
   33721 Tampere
   Finland
   Phone: +358-7180-08000
   Email: miska.hannuksela@nokia.com










Wang, et al.                 Standards Track                   [Page 86]

