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

guest271314 <guest271314@gmail.com> Sun, 27 December 2020 15:33 UTC

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Subject: [Cellar] Update specification language: CodecPrivate element MUST be set for H264 in Matroska
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Evidently CodecPrivate element being required/mandatory for H264 in
Matroska container is not clear nor conspicuous enough in the
standard/specification.

Cure that by conspicuously and unambiguously including wording in the
standard/specification that " CodecPrivate element MUST be set for H264 in
Matroska".

References:

https://gitlab.com/mbunkus/mkvtoolnix/-/issues/2986#note_474111881

> Yes, both require & expect it to be present as there's important data
stored there. One could go and assume certain defaults, and that might
actually work for certain files, but not in general. This isn't a bug, nor
a missing feature.

https://gitlab.com/mbunkus/mkvtoolnix/-/issues/2986#note_474135850

> Whether or not certain header elements (not just CodecPrivate) must be
set depends on the video codec. VP8 & VP9 don't require one, for example,
whereas AVC/h.264 & HEVC/h.265 do.

https://gitlab.com/mbunkus/mkvtoolnix/-/issues/2986#note_474137735

> We don't use RFC-style verbiage everywhere yet. The terms "CodecPrivate
contains…" pretty much states that the element is required for decoding.

Issue 1161944: CodecPrivate element is required for H264 in Matroska -
Chrome MediaRecorder does not set the element
https://bugs.chromium.org/p/chromium/issues/detail?id=1161944

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