[FFmpeg-devel] [PATCH] Add default stream flag

[Aurelien Jacobs]

Evgeniy Stepanov wrote:

> On Friday 29 February 2008 03:39:29 Aurelien Jacobs wrote:
> > Evgeniy Stepanov wrote:
> > > On Thursday 28 February 2008 23:49:15 Michael Niedermayer wrote:
> > > > On Thu, Feb 28, 2008 at 11:24:22PM +0300, Evgeniy Stepanov
> > > > wrote:
> > > > > Hi,
> > > > >
> > > > > this patch adds 'default_stream' flag to AVStream. Streams
> > > > > marked as default are to be selected for playback (or
> > > > > whatever else) if the user does not have any other preference
> > > > > (like language, or an exact stream id).
> > > > >
> > > > > This patch adds support for such streams in matroska muxer and
> > > > > demuxer. I don't know if there is similar functionality in
> > > > > other containers.
> > > >
> > > > nut of course ...
> > > >
> > > > > Is there a better place to put this information, without
> > > > > adding a new member to AVStream ?
> > > > >
> > > > > Maybe add an AVStream.flags with one bit of it occupied by
> > > > > default_stream flag ?
> > > >
> > > > This is better, but please call it int disposition; with
> > > > AV_DISPOSITION_DEFAULT
> > > > AV_DISPOSITION_DUB
> > > > AV_DISPOSITION_ORIGINAL
> > > > AV_DISPOSITION_COMMENT
> > > > AV_DISPOSITION_LYRICS
> > > > AV_DISPOSITION_KARAOKE
> > >
> > > Here. Both matroska and nut supported (I invented new disposition
> > > 'default' for nut, it is not in the spec). In ffmpeg.c,
> > > disposition is copied from ist to ost.
> > >
> > > [...]
> > >
> > > --- a/libavformat/matroskaenc.c
> > > +++ b/libavformat/matroskaenc.c
> > > @@ -549,6 +549,8 @@ static int mkv_write_tracks(AVFormatContext
> > > *s) else
> > >              put_ebml_string(pb, MATROSKA_ID_TRACKLANGUAGE,
> > > "und");
> > >
> > > +        put_ebml_uint(pb,
> > > MATROSKA_ID_TRACKFLAGDEFAULT, !!(st->disposition &
> > > AV_DISPOSITION_DEFAULT));
> >
> > IMO, don't write this uint if it's not needed:
> >
> >     if (st->disposition & AV_DISPOSITION_DEFAULT)
> >         put_ebml_uint(pb, MATROSKA_ID_TRACKFLAGDEFAULT, 1);
> >
> > Except that, matroska part is OK.
> 
> I considered this, but
> - it's written for every track in almost all mkvs out there;
> - mkvmerge always writes it.
> 
> So, just to be safe, for the sake of all demuxers whose authors did
> not the specification... And 4 bytes per stream is not that much.
> 
> And, surprise, the default value, according to spec, is 1.

Hum... Well, then it's fine.

Aurel