RTP Payload Format--- Packetization Modes

http://tools.ietf.org/html/rfc6184

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5.4. Packetization Modes

This memo specifies three cases of packetization modes: o Single NAL unit mode o Non-interleaved mode o Interleaved mode The single NAL unit mode is targeted for conversational systems that comply with ITU-T Recommendation H.241 [ 3] (see Section 12.1). The non-interleaved mode is targeted for conversational systems that may not comply with ITU-T Recommendation H.241. In the non-interleaved mode, NAL units are transmitted in NAL unit decoding order. The interleaved mode is targeted for systems that do not require very low end-to-end latency. The interleaved mode allows transmission of NAL units out of NAL unit decoding order. The packetization mode in use MAY be signaled by the value of the OPTIONAL packetization-mode media type parameter. The used packetization mode governs which NAL unit types are allowed in RTP payloads. Table 3 summarizes the allowed packet payload types for each packetization mode. Packetization modes are explained in more detail in Section 6. Table 3. Summary of allowed NAL unit types for each packetization mode (yes = allowed, no = disallowed, ig = ignore) Payload Packet Single NAL Non-Interleaved Interleaved Type Type Unit Mode Mode Mode ------------------------------------------------------------- 0 reserved ig ig ig 1-23 NAL unit yes yes no 24 STAP-A no yes no 25 STAP-B no no yes 26 MTAP16 no no yes 27 MTAP24 no no yes 28 FU-A no yes yes 29 FU-B no no yes 30-31 reserved ig ig ig Some NAL unit or payload type values (indicated as reserved in Table 3) are reserved for future extensions. NAL units of those types SHOULD NOT be sent by a sender (direct as packet payloads, as aggregation units in aggregation packets, or as fragmented units in FU packets) and MUST be ignored by a receiver. For example, the payload types 1-23, with the associated packet type "NAL unit", are Wang, et al. Standards Track [Page 16]

 
RFC 6184           RTP Payload Format for H.264 Video           May 2011


   allowed in "Single NAL Unit Mode" and in "Non-Interleaved Mode" but
   disallowed in "Interleaved Mode".  However, NAL units of NAL unit
   types 1-23 can be used in "Interleaved Mode" as aggregation units in
   STAP-B, MTAP16, and MTAP24 packets as well as fragmented units in FU-
   A and FU-B packets.  Similarly, NAL units of NAL unit types 1-23 can
   also be used in the "Non-Interleaved Mode" as aggregation units in
   STAP-A packets or fragmented units in FU-A packets, in addition to
   being directly used as packet payloads.

5.4. Packetization Modes

This memo specifies three cases of packetization modes: o Single NAL unit mode o Non-interleaved mode o Interleaved mode The single NAL unit mode is targeted for conversational systems that comply with ITU-T Recommendation H.241 [ 3] (see Section 12.1). The non-interleaved mode is targeted for conversational systems that may not comply with ITU-T Recommendation H.241. In the non-interleaved mode, NAL units are transmitted in NAL unit decoding order. The interleaved mode is targeted for systems that do not require very low end-to-end latency. The interleaved mode allows transmission of NAL units out of NAL unit decoding order. The packetization mode in use MAY be signaled by the value of the OPTIONAL packetization-mode media type parameter. The used packetization mode governs which NAL unit types are allowed in RTP payloads. Table 3 summarizes the allowed packet payload types for each packetization mode. Packetization modes are explained in more detail in Section 6. Table 3. Summary of allowed NAL unit types for each packetization mode (yes = allowed, no = disallowed, ig = ignore) Payload Packet Single NAL Non-Interleaved Interleaved Type Type Unit Mode Mode Mode ------------------------------------------------------------- 0 reserved ig ig ig 1-23 NAL unit yes yes no 24 STAP-A no yes no 25 STAP-B no no yes 26 MTAP16 no no yes 27 MTAP24 no no yes 28 FU-A no yes yes 29 FU-B no no yes 30-31 reserved ig ig ig Some NAL unit or payload type values (indicated as reserved in Table 3) are reserved for future extensions. NAL units of those types SHOULD NOT be sent by a sender (direct as packet payloads, as aggregation units in aggregation packets, or as fragmented units in FU packets) and MUST be ignored by a receiver. For example, the payload types 1-23, with the associated packet type "NAL unit", are Wang, et al. Standards Track [Page 16]

 
RFC 6184           RTP Payload Format for H.264 Video           May 2011


   allowed in "Single NAL Unit Mode" and in "Non-Interleaved Mode" but
   disallowed in "Interleaved Mode".  However, NAL units of NAL unit
   types 1-23 can be used in "Interleaved Mode" as aggregation units in
   STAP-B, MTAP16, and MTAP24 packets as well as fragmented units in FU-
   A and FU-B packets.  Similarly, NAL units of NAL unit types 1-23 can
   also be used in the "Non-Interleaved Mode" as aggregation units in
   STAP-A packets or fragmented units in FU-A packets, in addition to
   being directly used as packet payloads.