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

[James Almer]

On 3/2/2017 5:44 AM, Carl Eugen Hoyos wrote:
> 2017-03-02 0:26 GMT+01:00 James Almer <jamrial at gmail.com>:
>> On 3/1/2017 7:18 PM, Carl Eugen Hoyos wrote:
> 
>>>> This doesn't consider the CodecPrivate contents for FFV1 v3
>>>> and above. It's only valid for v1 and v2.
>>>
>>> Is this comment meant for the muxer or the demuxer part?
>>>
>>> How can I reproduce the issue you see?
>>> For me, everything works as specified for default strictness.
>>
>> 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.
> 
> Since this behaviour can only be produced with non-strict, I don't
> think it is of much relevance.

Strict experimental is only needed at the encoder level, not the muxer
level. This behavior can be reproduced just fine by remuxing existing
ffv1 v2 files into Matroska using the default strictness.

For that matter, Matroska (in V_MS/VFW/FOURCC mode), Nut and AVI
probably shouldn't store v2 extradata either as mentioned by the spec,
but they currently seem to do it.

> Anyway, this is removed from the current patch.

Fair enough.

> 
> Carl Eugen
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