[Cellar] Fwd: Update specification language: CodecPrivate element MUST be set for H264 in Matroska

[guest271314 <[e-mail]>]

---------- Forwarded message ---------
From: guest271314 <[e-mail]>
Date: Sun, Dec 27, 2020 at 8:36 AM
Subject: Re: [Cellar] Update specification language: CodecPrivate element
MUST be set for H264 in Matroska
To: Jerome Martinez <[e-mail]>


Alternatively, if your conclusion is that the specification/standard is
clear right now, can you kindly inform the Chrome authors of the same, and
their omission of the element is non-compliant with the
specification/standard at
https://bugs.chromium.org/p/chromium/issues/detail?id=601636#c_ts1609079978
so that there will be no quarter for confusion as to Chrome MediaRecorder
implementation being non-conformant with the sections that you cited.

Either way Chrome authors need to be aware of this issue from the canonical
source.

On Sun, Dec 27, 2020 at 8:15 AM Jerome Martinez <[e-mail]>
wrote:

> On 27/12/2020 16:33, guest271314 wrote:
> > Cure that by conspicuously and unambiguously including wording in the
> > standard/specification that " CodecPrivate element MUST be set for
> > H264 in Matroska".
>
> CodecPrivate in Matroska general specification is not mandatory, as this
> status depends on the coding format (mandatory for H.264, not mandatory
> for MPEG-2 etc).
>
> From
>
> https://github.com/ietf-wg-cellar/matroska-specification/blob/master/codec_specs.md#v_mpeg4isoavc
> "The Private Data contains a AVCDecoderConfigurationRecord structure,
> [...]"
> This is not the IETF "MUST" but seems clear (affirmative sentence) that
> CodecPrivate is mandatory in the case of the H.264 mapping.
>
> Do you mean that we should be even more clear in 2 places?
> - in CodecPrivate definition, something like CodecPrivate is mandatory
> if specified as such ("MUST") in the corresponding codec mapping
> specification.
> - in H.264 codec mapping definition, something like The CodecPrivate
> block MUST contain a AVCDecoderConfigurationRecord structure [...]
>
> Jérôme
>
>