RTP Payload Format for Visual Volumetric Video-based Coding (V3C)

3.1.1. General

This document uses the definitions of [ISO.IEC.23090-5]. Section 3.1.2 below lists relevant definitions from [ISO.IEC.23090-5] for convenience.¶

3.1.2. Definitions from the V3C specification

atlas: collection of 2D bounding boxes and their associated information placed onto a rectangular frame and corresponding to a volume in 3D space on which volumetric data is rendered.¶

atlas bitstream: sequence of bits that forms the representation of atlas frames and associated data forming one or more coded atlas sequences.¶

atlas coding layer NAL unit: collective term for coded atlas tile layer NAL units and the subset of NAL units that have reserved values of nal_unit_type that are classified as being of type class equal to ACL in this document.¶

atlas frame: 2D rectangular array of atlas samples onto which patches are projected and additional information related to the patches, corresponding to a volumetric frame.¶

attribute: scalar or vector property optionally associated with each point in a volumetric frame such as colour, reflectance, surface normal, timestamps, material ID, etc.¶

coded atlas sequence: sequence of coded atlas access units, in decoding order, of an IRAP coded atlas access unit, followed by zero or more coded atlas access units that are not IRAP coded atlas access units, including all subsequent access units up to but not including any subsequent coded atlas access unit that is an IRAP coded atlas access unit.¶

coded atlas access unit: set of atlas NAL units that are associated with each other according to a specified classification rule, are consecutive in decoding order, and contain all atlas NAL units pertaining to one particular output time.¶

coded visual volumetric video-based coding (V3C) sequence: sequence of V3C atlas and video sub-bitstream(s) identified and separated by appropriate delimiters, required to start with a VPS, included in at least one V3C unit or provided through external means.¶

network abstraction layer unit: syntax structure containing an indication of the type of data to follow and bytes containing that data in the form of an RBSP.¶

patch: rectangular region within an atlas associated with volumetric information.¶

raw byte sequence payload: syntax structure containing an integer number of bytes that is encapsulated in a NAL unit and that is either empty or has the form of a string of data bits containing syntax elements followed by an RBSP stop bit and zero or more subsequent bits equal to 0.¶

tile: independently decodable rectangular region of an atlas frame.¶

visual volumetric video-based coding (V3C) atlas sub-bitstream: extracted sub-bitstream from the V3C bitstream containing whole or portion of an atlas bitstream.¶

visual volumetric video-based coding (V3C) video sub-bitstream: extracted sub-bitstream from the V3C bitstream containing whole or portion of a video bitstream.¶

visual volumetric video-based coding (V3C) component: atlas, occupancy, geometry, or attribute of a particular type that is associated with a V3C volumetric content representation.¶

visual volumetric video-based coding (V3C) parameter set: syntax structure containing syntax elements that apply to zero or more entire CVSs and may be referred to by syntax elements found in the V3C unit header.¶

volumetric frame: set of 3D points specified by their cartesian coordinates and zero or more corresponding sets of attributes at a particular time instance.¶

4.3.1. General

In V3C bitstream the atlas component is identified by vuh_unit_type equal to V3C_AD, or V3C_CAD in case of common atlas data, in the V3C unit header. The V3C atlas component consists of atlas NAL units that define header and payload pairs, see Section 4.3.2. V3C video components are identified by vuh_unit_type equal to V3C_OVD, V3C_GVD, V3C_AVD, and V3C_PVD. V3C video components can be further differentiated by other values in the V3C unit header such as vuh_attribute_index, vuh_attribute_partition_index, vuh_map_index and vuh_auxiliary_video_flag. By mapping V3C parameter set information to vuh_attribute_index, a V3C decoder identifies which attribute a given V3C video component contains, e.g., colour.¶

The information supplied by V3C unit header should be provided in one form or another to a V3C decoder, e.g., as part of SDP as described in this memo in Section 9. The four-byte V3C unit header syntax and semantics are copied below as defined in [ISO.IEC.23090-5], but the syntax is subject to change. Implementations should always refer to the latest specification of [ISO.IEC.23090-5]. The syntax of four-byte V3C unit header is provided here for informative purposes only.¶

v3c_unit_header( ) {
 unsigned int(5) vuh_unit_type;
 if( vuh_unit_type == V3C_AVD || vuh_unit_type == V3C_GVD ||
   vuh_unit_type == V3C_OVD || vuh_unit_type == V3C_AD ||
   vuh_unit_type == V3C_CAD || vuh_unit_type == V3C_PVD ) {
   unsigned int(4) vuh_v3c_parameter_set_id;
  }
  if( vuh_unit_type == V3C_AVD || vuh_unit_type == V3C_GVD ||
    vuh_unit_type == V3C_OVD || vuh_unit_type == V3C_AD ||
    vuh_unit_type == V3C_PVD ) {
    unsigned int(6) vuh_atlas_id;
  }
  if( vuh_unit_type == V3C_AVD ) {
    unsigned int(7) vuh_attribute_index;
    unsigned int(5) vuh_attribute_partition_index;
    unsigned int(4) vuh_map_index;
    unsigned int(1) vuh_auxiliary_video_flag;
  }
  else if( vuh_unit_type == V3C_GVD ) {
    unsigned int(4) vuh_map_index;
    unsigned int(1) vuh_auxiliary_video_flag;
    bit(12) vuh_reserved_zero_12bits;
  }
  else if( vuh_unit_type == V3C_OVD || vuh_unit_type == V3C_AD ||
      vuh_unit_type == V3C_PVD) {
    bit(17) vuh_reserved_zero_17bits;
  }
  else if( vuh_unit_type == V3C_CAD ) {
    bit(23) vuh_reserved_zero_23bits;
  }
  else {
    bit(27) vuh_reserved_zero_27bits;
  }
}

vuh_unit_type indicates the V3C unit type for the V3C component as specified in [ISO.IEC.23090-5]. As a convenience, the mapping table from vuh_unit_type values to semantics is copied below in Table 1.¶

vuh_v3c_parameter_set_id specifies the value of vps_v3c_parameter_set_id for the active V3C VPS.¶

vuh_atlas_id specifies the ID of the atlas that corresponds to the current V3C unit.¶

vuh_attribute_index indicates the index of the attribute data carried in the Attribute Video Data unit.¶

vuh_attribute_partition_index indicates the index of the attribute dimension group carried in the attribute video data unit.¶

vuh_map_index when present indicates the map index of the current geometry or attribute stream. When not present, the map index of the current geometry or attribute sub-bitstream is derived based on the type of the sub-bitstream.¶

vuh_auxiliary_video_flag equal indicates if the associated geometry or attribute video data unit is a RAW and/or EOM coded points video only sub-bitstream.¶

4.3.2. Atlas NAL units

Atlas NAL unit (nal_unit(NumBytesInNalUnit)) is a byte-aligned syntax structure defined by [ISO.IEC.23090-5] to carry atlas data. Atlas NAL unit always contains a 16-bit NAL unit header (nal_unit_header()), which indicates among other things the type of the NAL unit (nal_unit_type). The payload of a NAL unit refers to the NAL unit excluding the NAL unit header. The Atlas NAL unit syntax and semantics are copied here as defined in [ISO.IEC.23090-5].¶

nal_unit_header(){
    bit(1) nal_forbidden_zero_bit;
    bit(6) nal_unit_type;
    bit(6) nal_layer_id;
    bit(3) nal_temporal_id_plus1;
}
nal_unit(NumBytesInNalUnit){
    nal_unit_header();
    NumBytesInRbsp = 0;
    for( i = 2; i < NumBytesInNalUnit; i++ )
      bit(8) rbsp_byte[ NumBytesInRbsp++ ];
}

nal_forbidden_zero_bit MUST be equal to 0. (F)¶

nal_unit_type indicates the type of the RBSP data structure contained in the NAL unit (NUT)¶

nal_layer_id indicates the identifier of the layer to which an ACL NAL unit belongs or the identifier of a layer to which a non-ACL NAL unit applies. (NLI)¶

nal_temporal_id_plus1 minus 1 indicates a temporal identifier for the NAL unit. The value of nal_temporal_id_plus1 MUST NOT be equal to 0. (TID)¶

5.4.1. General

Three different types of RTP packet payload structures are specified. A receiver can identify the payload structure by the first two bytes of the RTP packet payload, which co-serves as the RTP payload header. These two bytes are always structured as a NAL unit header. The NAL unit type field indicates which structure is present in the payload.¶

The three different payload structures are as follows:¶

• Single NAL Unit Packet: Contains a single NAL unit in the payload. This payload structure is specified in Section 5.4.2.¶

• Aggregation Packet: Contains multiple NAL units in a single RTP payload. This payload structure is specified in Section 5.4.3.¶

• Fragmentation Unit: Contains a subset of a single NAL unit. This payload structure is specified in Section 5.4.4.¶

NOTE: (informative) This memo does not limit the size of NAL units encapsulated in NAL unit packets and fragmentation units. [ISO.IEC.23090-5] does not restrict the maximum size of a NAL unit directly either. Instead, a NAL unit sample stream format may be used, which provides flexibility to signal NAL unit size up to UINT64_MAX bytes.¶

5.4.2. Single NAL unit packet

Single NAL unit packet contains exactly one NAL unit, and consists of an RTP payload header and following conditional fields: 16-bit DONL and 16-bit v3c-tile-id. The rest of the payload data contain the NAL unit payload data (excluding the NAL unit header). Single NAL unit packet MUST only contain atlas NAL units of the types defined in Table 4 of [ISO.IEC.23090-5]. The structure of the single NAL unit packet is shown below 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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |      RTP payload header       |      DONL (conditional)       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
  |      v3c-tile-id (cond)       |                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
  |                                                               |
  |                        NAL unit data                          |
  |                                                               |
  |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                               :...OPTIONAL RTP padding        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

RTP payload header MUST be an exact copy of the NAL unit header of the contained NAL unit.¶

A NAL unit stream composed by de-packetizing single NAL unit packets in RTP sequence number order MUST conform to the NAL unit decoding order, when DONL is not present.¶

The DONL field, when present, specifies the value of the 16-bit 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 DONL 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.¶

The v3c-tile-id field, when present, specifies the 16-bit tile identifier for the NAL unit, as signalled in V3C atlas tile header defined in [ISO.IEC.23090-5]. If sprop-v3c-tile-id-pres is equal to 1 and RTP payload header NUT is in range 0-35, inclusive, the v3c-tile-id field MUST be present. Otherwise, the v3c-tile-id field MUST NOT be present.¶

NOTE: (informative) Only values for NAL unit type (NUT) in range 0-35, inclusive, are allocated for atlas tile layer data in [ISO.IEC.23090-5].¶

5.4.3. Aggregation packet

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

Aggregation packets MAY be used wrap multiple NAL units belonging to the same access unit in a single RTP payload. The first two bytes of the AP MUST contain RTP payload header. The NAL unit type (NUT) for the NAL unit header contained in the RTP payload header MUST be equal to 56, which falls in the unspecified range of the NAL unit types defined in [ISO.IEC.23090-5]. AP MAY contain a conditional v3c-tile-id field. AP MUST contain two or more aggregation units. The structure of AP is 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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  RTP payload header (NUT=56)  |      v3c-tile-id (cond)       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                                                               |
  |                  Two or more aggregation units                |
  |                                                               |
  |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                               :...OPTIONAL RTP padding        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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 NUT field MUST be equal to 56. The value of NLI MUST be equal to the lowest value of NLI of all the aggregated NAL units. The value of TID MUST be the lowest value of TID of all the aggregated NAL units.¶

All ACL NAL units in an aggregation packet have the same TID value since they belong to the same access unit. However, the packet MAY contain non-ACL NAL units for which the TID value in the NAL unit header MAY be different than the TID value of the ACL NAL units in the same AP.¶

The v3c-tile-id field, when present, specifies the 16-bit tile identifier for all ACL NAL units in the AP. If sprop-v3c-tile-id-pres is equal to 1, the v3c-tile-id field MUST be present. Otherwise, the v3c-tile-id field MUST NOT be present.¶

AP MUST carry at least two aggregation units (AU) and can carry as many aggregation units as necessary. However, the total amount of data in an AP 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. The structure of the AU depends both on the presence of the decoding order number, the sequence order of the AU in the AP and the presence of v3c-tile-id field. The structure of an AU is 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)  /  DONL (cond)  |      v3c-tile-id (cond)       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
  |            NALU size          |                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
  |                                                               |
  |                            NAL unit                           |
  |                                                               |
  |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

If sprop-max-don-diff is greater than 0 for any of the RTP streams, an AU begins with the DOND / DONL field. The first AU in the AP contains DONL field, which specifies the 16-bit value of the decoding order number of the aggregated NAL unit. The variable DON for the aggregated NAL unit is derived as equal to the value of the DONL field. All subsequent AUs in the AP MUST contain an (8-bit) DOND field, which 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. 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.¶

When sprop-max-don-diff is equal to 0 for all the RTP streams, DOND / DONL fields MUST NOT be present in an aggregation unit. The aggregation units MUST be stored in the aggregation packet so that the decoding order of the containing NAL units is preserved. This means that the first aggregation unit in the aggregation packet SHOULD contain the NAL unit that SHOULD be decoded first.¶

If sprop-v3c-tile-id-pres is equal to 2 and the AU NAL unit header type is in range 0-35, inclusive, the 16-bit v3c-tile-id field MUST be present in the aggregation unit after the conditional DOND/DONL field. Otherwise v3c-tile-id field MUST NOT be present in the aggregation unit.¶

The conditional fields of the aggregation unit are followed by a 16-bit NALU size field, which provides the size of the NAL unit (in bytes) in the aggregation unit. The remainder of the data in the aggregation unit SHOULD contain the NAL unit (including the unmodified NAL unit header).¶

5.4.4. Fragmentation unit

Fragmentation Units (FUs) are introduced to enable fragmenting a single NAL unit into multiple RTP packets, possibly without co-operation or knowledge of the 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. Aggregation packets MUST NOT be fragmented. FUs MUST NOT be nested; i.e., an FU MUST NOT contain a subset of another FU. The RTP header timestamp of an RTP packet carrying an FU is set to the NALU-time of the fragmented NAL unit.¶

A FU consists of an RTP payload header with NUT equal to 57, an 8-bit FU header, a conditional 16-bit DONL field, a conditional 16-bit v3c-tile-id field and an FU payload. The structure of an FU is illustrated below in Figure 7.¶

   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 payload header (NUT=57)  |   FU header   |  DONL (cond)  |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
  |  DONL (cond)  |    v3c-tile-id (cond)         |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
  |                                                               |
  |                          FU payload                           |
  |                                                               |
  |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                               :...OPTIONAL RTP padding        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The fields in the RTP payload header are set as follows. The NUT field MUST be equal to 57. The rest of the fields MUST be equal to the fragmented NAL unit.¶

The FU header consists of an S bit, an E bit, and a 6-bit FUT field. The structure of FU header is illustrated below in Figure 8.¶

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

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.¶

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.¶

The field FUT MUST be equal to the nal_unit_type field of the fragmented NAL unit.¶

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 DONL field, when present, specifies the value of the 16-bit 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.¶

The v3c-tile-id field, when present, specifies the 16-bit tile identifier for the fragmented NAL unit. If sprop-v3c-tile-id-pres is equal to 1, FUT is in range 0-35, and the S bit is equal to 1, the v3c-tile-id field MUST be present after the conditional DONL field. Otherwise, the v3c-tile-id field MUST NOT be present.¶

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, NLI, and TID fields of the RTP payload headers of the FUs and the FUT field of the FU header. 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.¶

5.4.5. Example of fragmentation unit (informative)

This example illustrates how fragmentation unit may be used to divide one NAL unit into two RTP packets. The Figure 9 depicts the structure of the first packet with the first part of the fragmented NAL unit.¶

   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             |
  |                             ....                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  RTP payload header (NUT=57)  |1|0|    FUT    |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
  |                                                               |
  |                          FU payload                           |
  |                                                               |
  |                                                               |
  |                                                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The Figure 10 visualizes the structure of the second packet with the rest of the fragmented NAL unit.¶

   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             |
  |                             ....                              |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |  RTP payload header (NUT=57)  |0|1|    FUT    |               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
  |                                                               |
  |                          FU payload                           |
  |                                                               |
  |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                               :...OPTIONAL RTP padding        |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

9.2.1. For V3C atlas components

• The media name in the "m=" line of SDP MUST be application.¶

• The encoding name in the "a=rtpmap" line of SDP MUST be v3c¶

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

• The OPTIONAL parameters sprop-v3c-atlas-data, sprop-v3c-common-atlas-data, sprop-v3c-sei, sprop-v3c-tile-id, sprop-v3c-tile-id-pres, 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.¶

• The OPTIONAL parameters sprop-v3c-unit-header, sprop-v3c-unit-type, sprop-v3c-vps-id, sprop-v3c-atlas-id, sprop-v3c-attr-idx, sprop-v3c-attr-part-idx, sprop-v3c-map-idx, sprop-v3c-aux-video-flag, sprop-max-don-diff, sprop-v3c-parameter-set, v3c-ptl-level-idc, v3c-ptl-tier-flag, v3c-ptl-codec-idc, v3c-ptl-toolset-idc, v3c-ptl-rec-idc, when present, MUST be included in the "a=v3cfmtp" line of SDP. This parameter is expressed as a media type string, in the form of a semicolon-separated list of parameter=value pairs.¶

The OPTIONAL parameters, when present in the V3C atlas component media line format parameters attribute, specify values that are valid for the coded V3C sequence until a new value is received in-band. Some OPTIONAL parameters, like sprop-v3c-parameter-set or sprop-v3c-unit-header, can't be carried in-band in the atlas stream and may thus be considered static for the session. The carriage of V3C payload format parameters in "a=fmtp" and "a=v3cfmtp" attributes is separated by logical context, where "a=fmtp" consists atlas level media format parameters and "a=v3cfmtp" contains V3C level media format parameters.¶

An example of media representation corresponding to atlas data component (V3C_AD), where static V3C parameter set and V3C unit header is carried out-of-band in SDP, is as follows:¶

  m=application 49170 RTP/AVP 98
  a=rtpmap:98 v3c/90000
  a=fmtp:98 sprop-v3c-tile-id=0,1
  a=v3cfmtp:sprop-v3c-unit-header=CAAAAA==;v3c-ptl-tier-flag=1;
    sprop-v3c-parameter-set=AQD/AAAP/zwAAAAAADwIAQ5BwAAOADjgQAADkA==

9.2.2. For V3C video components

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

• The encoding name in the "a=rtpmap" line of SDP can be any video subtype, e.g., H.264, H.265, H.266 etc.¶

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

• The OPTIONAL parameters sprop-v3c-unit-header, sprop-v3c-unit-type, sprop-v3c-vps-id, sprop-v3c-atlas-id, sprop-v3c-attr-idx, sprop-v3c-attr-part-idx, sprop-v3c-map-idx, sprop-v3c-aux-video-flag, sprop-max-don-diff, sprop-v3c-parameter-set, sprop-v3c-atlas-data, sprop-v3c-common-atlas-data, sprop-v3c-sei, sprop-v3c-tile-id, sprop-v3c-tile-id-pres, v3c-ptl-level-idc, v3c-ptl-tier-flag, v3c-ptl-codec-idc, v3c-ptl-toolset-idc, v3c-ptl-rec-idc, when present, MUST be included in the "a=v3cfmtp" line of SDP. This parameter is expressed as a media type string, in the form of a semicolon-separated list of parameter=value pairs.¶

The OPTIONAL parameters, when present in the video media line V3C format parameters ("v3cfmtp") attribute, specify values that are considered static for the session.¶

An example of media representation corresponding to occupancy video component (V3C_OVD) in SDP is as follows:¶

  m=video 49170 RTP/AVP 99
  a=rtpmap:99 H265/90000
  a=fmtp:99 sprop-max-don-diff=0;
  a=v3cfmtp:sprop-v3c-unit-header=EAAAAA==

Below is an example of media representation corresponding to packed video component (V3C_PVD), where static V3C parameter set, atlas data and common atlas data are carried out-of-band in SDP. The values are considered static for the session, as they can't be signaled in-band in the video stream.¶

  m=video 49170 RTP/AVP 99
  a=rtpmap:99 H265/90000
  a=v3cfmtp:sprop-v3c-unit-header=KAAAAA==;
    sprop-v3c-parameter-set=AUH/AAAP/zwAAAAAACgIAtEAgQLAIAAUQBACWAM5Q
    EDgQCAIAAAAABP8CzwAAAAAAAAAQAAAtAE/wLPAAAAAAAg=;
    sprop-v3c-atlas-data=SAGAFAQBaKjuXgABQEKA,SgHmIA==,LgFoDOAFAABaAA
    AAAAA+;
    sprop-v3c-common-atlas-data=YAEHgFA=,YgEAMAAAC/B0qcvv/Dbr/pTvb8oq
    fhC5JQVS9jn7kAQT/As9EFyrjRBcmxEQe+j5DuGbTT9mZmZAQAAAoA==