[FFmpeg-devel] [PATCH] avformat/matroskaenc: add matroska subtitle muxer (.mks)

[Andreas Rheinhardt]

James Almer:
> On 4/4/2020 3:00 PM, Jan Chren (rindeal) wrote:
>> On Sat, 4 Apr 2020 at 16:32, Andreas Rheinhardt
>> <andreas.rheinhardt at gmail.com> wrote:
>>> What is the aim of your patch? If it is simply making sure that using
>>> the mks extension autoselects the Matroska muxer,
>>
>> That's correct.
>>
>>> then adding "mks" to
>>> the list of extensions of the ordinary Matroska muxer would be enough.
>>> (Notice that using mka for files with audio, but without video or mks
>>> for subtitle-only files is just a convention; putting something else
>>> than indicated by the extension in the files does not make them less
>>> spec-compliant.)
>>
>> Should I create a new patch which removes the audio muxer and just
>> adds `mka` and `mks` extensions to the ordinary muxer?
>> Or is there some reason why a dedicated audio muxer must exist,
>> whereas a subtitle muxer does not?
> 
> Is there a mimetype specific for .mks? If so, then a separate demuxer
> would be acceptable. Otherwise, simply adding the extension to the
> existing matroska muxer and adding stream checks to mkv_init() should
> suffice.
> 
> In any case, your patch is apparently not correct as it's missing all
> the allowed codec ids in AVCodec.codec_tag, and/or defining an
> AVCodec.query_codec function to only accept subtitle codecs.

Using mks is actually just a convention, so putting only subtitles into
it should not be enforced (just as is with the Matroska audio muxer). If
I am not mistaken, then a separate muxer would only help with stream
auto-selection (i.e. it would make -map in FFmpeg cli superfluous).

- Andreas