[FFmpeg-devel] [PATCH]lavf/matroska: Support codec id V_FFV1 for FFV1.

Tobias Rapp t.rapp at noa-archive.com
Thu Mar 2 16:47:36 EET 2017

On 02.03.2017 15:22, James Almer wrote:
> On 3/2/2017 6:28 AM, Nicolas George wrote:
>> Le primidi 11 ventôse, an CCXXV, James Almer a écrit :
>>> Ah, i see there's generic code to read and write CodecPrivate elements
>>> to and from raw extradata for native codecids where no special handling
>>> is required.
>>> In any case, the spec says
>>> "For FFV1 versions 2 or less, Private Data SHOULD NOT be written."
>>> The ffv1 encoder creates extradata for v2 and newer, so the muxer
>>> should have a custom case for ffv1 in order to detect v2 streams and
>>> avoid writing said extradata.
>> I have not looked myself at the situation, I only read what you wrote
>> her. According to it, it seems here the FFV1 encoder is violating the
>> specification and needs to be fixed.
> I can't say if the encoder exporting extradata for version 2 is right or
> wrong, as muxers or bsfs could still use it for whatever reason, but at
> least according to the draft ffv1 spec by Michael, it's to be stored at
> the container level *only* on versions 3 and above.
> https://tools.ietf.org/html/draft-niedermayer-cellar-ffv1-01#section-4.1

The IETF draft explicitly excludes to specify FFV1 version 2:

IIRC there have been some edits to remove references to version 2 in the 
IETF draft. In the older document at 
http://www.ffmpeg.org/%7Emichael/ffv1.html#configuration-record the 
section contains "version >= 2".


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