Re: [Cellar] AV1 mapping update

[Steve Lhomme <[e-mail]>]

>>> So maybe your proposal should be added. We'll gain a bit of weight but
>>> it's safer.
>>>
>> My wording would be:
>> "Upon seeking to a keyframe the player/demuxer MUST prepend the `Block`
>> with the `Sequence Header OBU` contained in the `CodecPrivate`.
>> A muxer MUST make sure that the correct `Sequence Header OBU` is in
>> force both during linear access and also after seeking to a keyframe
>> `Block`. So in particular a keyframe `Block` where a `Sequence Header
>> OBU` that is not bit-identical to the one in the `CodecPrivate` is in
>> force for the decoding of the first frame contained in said `Block` MUST
>> contain the `Sequence Header OBU` that is in force for the decoding of
>> the first frame contained in said `Block` in front of the first frame
>> contained in said `Block`."
>>
>> One could also relax this a bit and only make the correct linear access
>> a MUST and the rest a SHOULD. This might be useful for applications
>> where seeking isn't desired (although it really should be included even
>> for those scenarios to support resuming playback after a transmission
>> error).
>
> OK, I'll try to add something for seeking.

Actually we already have it in the Segment Restrictions:

Given a `Sequence Header OBU` can be omitted from a `Block` if
__[decoder_model_info_present_flag]__ is 0 and it is bit identical to
the one found in `CodecPrivate`, when seeking to a keyframe, that
omitted `Sequence Header OBU` MUST be added back to the bitstream for
compliance with the Random Access Decoding section of the [AV1
Specifiations](#av1-specifications).


-- 
Steve Lhomme
Matroska association Chairman