[FFmpeg-devel] [PATCH 3/4] avformat/oggenc: make Vorbis audio the only default for ogg muxer

[Michael Niedermayer]

On Fri, Jul 08, 2016 at 12:08:14PM -0300, James Almer wrote:
> On 7/8/2016 4:22 AM, Michael Niedermayer wrote:
> > On Thu, Jul 07, 2016 at 11:02:30PM -0300, James Almer wrote:
> >> On 7/7/2016 10:55 PM, Michael Niedermayer wrote:
> >>> On Wed, Jul 06, 2016 at 08:25:26PM -0300, James Almer wrote:
> >>>> While not enforced, RFC 5334 mentions that the .ogg extension should
> >>>> be used for Vorbis audio files only.
> >>>>
> >>>> Signed-off-by: James Almer <jamrial at gmail.com>
> >>>> ---
> >>>> This patch turns the ogg muxer into an audio only muxer to follow
> >>>> the RFC's recommendation. The next patch in the set adds a new ogv
> >>>> muxer to properly deal with video files.
> >>>>
> >>>> I doubt anyone out there tries to mux theora video using the .ogg
> >>>> extension (even ffmpeg2theora seems to default to .ogv), so it's
> >>>> unlikely it will affect people's normal workflow.
> >>>> But if someone is against it then this patch can either be dropped
> >>>> or changed to only remove flac from the defaults. That way video
> >>>> can still be muxed.
> >>>>
> >>>> I personally prefer to apply this patch as is, though.
> >>>>
> >>>>  libavformat/oggenc.c | 4 +---
> >>>>  1 file changed, 1 insertion(+), 3 deletions(-)
> >>>
> >>> breaks fate
> >>
> >> Yes, forgot to run fate for this set. It's caused by the fact the ogg
> >> muxer can't mux video streams anymore after this patch.
> >>
> >> I want to know if the actual change is acceptable first, then I'll
> >> resend the set with fate tests updated to use ogv muxer and similar
> >> changes.
> > 
> > making it impossible to mux video into .ogg seems a bit strange and
> > unexpected to me. Thats just my personal oppinion, iam not blocking
> > this ...
> 
> My intention is to remove the default behavior of trying to mux video
> into .ogg extension files, which as the RFC states is meant for Vorbis
> audio. Any combination of Video + Audio and/or Subtitles is meant to
> use the .ogv extension and video/ogg mimetype.
> 

> I couldn't find a way to remove that default behavior that doesn't
> forbid muxing video when using the Ogg Muxer altogether. If you know
> how then I'm happy to use it because my objective is not to remove
> functionality to the muxer, even if said funcionality will be
> available in the Ogv muxer, but to make sure it doesn't mux content it
> ideally shouldn't unless explicitly told.
> Ogg, Oga, Speex, Opus and now Ogv are all aliases to the same
> underlying muxer after all.

ff_ogg_muxer should implement query_codec()
this could through avformat_query_codec() check if a specific video
codec is supported

ffmpeg would probably need to be modified to check this
i think its around line 2050 in ffmpeg_opt.c
dont know if thats the only change needed


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Everything should be made as simple as possible, but not simpler.
-- Albert Einstein
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