[FFmpeg-devel] [PATCH 01/17] avformat/mxfenc: Auto-insert h264_mp4toannexb BSF if needed

[Andreas Rheinhardt]

Tomas Härdin:
> tis 2021-11-09 klockan 22:07 +0100 skrev Andreas Rheinhardt:
>> Tomas Härdin:
>>> tis 2021-11-09 klockan 18:34 +0100 skrev Andreas Rheinhardt:
>>>> The mxf and mxf_opatom muxer expect H.264 in Annex B format.
>>>>
>>>> Signed-off-by: Andreas Rheinhardt
>>>> <andreas.rheinhardt at outlook.com>
>>>> ---
>>>> The check here is taken from mpegtsenc.
>>>
>>> You didn't think to make both muxers share code instead of copy-
>>> pasting?
>>>
>>
>> Well, I can share it. The problem is just that I didn't really know
>> where it belongs: mux.c? utils.c? A new file?
> 
> A new file probably, say libavformat/annexb.c
> 
> Do we ever need to be able to do this kind of stuff in lavc? In that
> case it could maybe live there. But that again increases coupling
> between the two libs..
> 

lavc does not have AVStreams or AVFormatContexts, so sharing code would
be absolutely impossible anyway. But one can share ideas: Using a bsf to
prepare data for a decoder is also done for certain decoders; see
AVCodec.bsfs. These bitstream filters are applied unconditionally and
are therefore supposed to detect themselves whether they should do
something or whether the data already has the desired form. I am unsure
whether this is a better approach; doing the same in lavf would add a
problem that lavc does not have: There would be a copy of every
non-refcounted packet when using av_write_frame().

- Andreas