Clarify normative aspects of TS header and AF fields

AOMediaCodec / av1-mpeg2-ts

Official specification of the AOM group for the carriage of AV1 in MPEG-2 Transport Stream

https://aomediacodec.github.io/av1-mpeg2-ts/

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Clarify normative aspects of TS header and AF fields #16

Open cconcolato opened 2 years ago

cconcolato commented 2 years ago

The DVB draft specification for AV1 mentions that:

payload_unit_start_indicator shall be set to 1
adaptation_field_control bits shall be set to "11"
The random_access_indicator shall be set to 1 when the PES packet contains an AV1 KeyFrame
The elementary_stream_priority_indicator and intra frame interact

It's unclear why these statements are not in the AV1-MPEG-2 TS specification. Could these be different outside of DVB environments? In any cases, the specification should talk about these fields: either to mandate the behavior or to indicate that the behavior can vary depending on application environments.

cconcolato commented 2 years ago

Current DVB text is: and

tbiat commented 2 years ago

payload_ ==> It's implicit and obvious. adaptationfield... ==> dvb mandates the adaptation field for random access AV1 DVB_RAP, we might not need it for other TS-based applications. Decision : share the DVB spec part related to this with the group. Revisit next week.

tbiat commented 1 year ago

We don't want RAP in this spec to conflict with AV1 DVB-RAP. Put a note : recommended practice / 'should contain'. Decision : take offline with Cyril. Propose a wording by email for approval.

cconcolato commented 1 year ago

The spec says:

A PES shall encapsulate one, and only one, AV1 access unit as defined in clause 4.3. We could add a note that says "as a consequence, the PUSI is set to 1"

The spec does neither mention 'adaptation_field_control' nor 'random_access_indicator', not even "random". We should at least have: "When the random access indicator is set to 1, the AV1 access unit shall contain an AV1 Key Frame".