[FFmpeg-devel] [PATCH] RealMedia muxer: support audio codecs other than AC-3

[Michael Niedermayer]

On Sat, May 08, 2010 at 09:15:30AM +0200, Francesco Lavra wrote:
> On Mon, 2010-05-03 at 18:39 +0200, Michael Niedermayer wrote:
> > On Mon, May 03, 2010 at 03:47:12PM +0100, M?ns Rullg?rd wrote:
> > > "Ronald S. Bultje" <rsbultje at gmail.com> writes:
> [...]
> > > > I'm OK with doing it if codec_id is unset (CODEC_ID_NONE). In any
> > > > other case, codec_tag should be ignored (imo) and if codec_id is not
> > > > in our table, we should error out. This way, we force ourselves to add
> > > > the *correct* tag for each codec_id, rather than taking the AVI fourcc
> > > > and probably ending up creating files only mplayer can playback.
> > > 
> > > +1
> > 
> > this breaks stream copy of old xvid and some mpeg4 variants like XVIX
> > and ump4
> > iam thus not in favor of it
> > what you 2 can do if you like to improve the situation is to implement the
> > FIXME below from libavformat/utils.c
> > 
> >  if(s->oformat->codec_tag){
> >     if(st->codec->codec_tag){
> >         //FIXME
> >         //check that tag + id is in the table
> >         //if neither is in the table -> OK
> >         //if tag is in the table with another id -> FAIL
> >         //if id is in the table with another tag -> FAIL unless strict < ?
> >     }else
> >         st->codec->codec_tag= av_codec_get_tag(s->oformat->codec_tag, st->codec->codec_id);
> > }
> > 
> > I understand you want to fail in a broader set of cases and iam not
> > even saying iam neccessarily against that but i think we first should
> > implement the cases we agree about. Once thats done we can discuss
> > the remaining cases
> 
> I'm not Ronald nor Mans, but I think the attached does what you ask for.
> I chose strict < normal as the last condition, hope that's fine.
> 

>  utils.c |   19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 6e0962390aa3c5c4a1d7182b084b5602bf7112c9  utils.patch
> Index: libavformat/utils.c
> ===================================================================
> --- libavformat/utils.c	(revision 23056)
> +++ libavformat/utils.c	(working copy)
> @@ -2616,14 +2616,27 @@
>          }
>  
>          if(s->oformat->codec_tag){
> +            unsigned int tag = av_codec_get_tag(s->oformat->codec_tag,
> +                                                st->codec->codec_id);
> +
>              if(st->codec->codec_tag){
> -                //FIXME
>                  //check that tag + id is in the table
>                  //if neither is in the table -> OK
>                  //if tag is in the table with another id -> FAIL
> -                //if id is in the table with another tag -> FAIL unless strict < ?
> +                //if id is in the table with another tag -> FAIL unless strict < normal
> +                enum CodecID id = av_codec_get_id(s->oformat->codec_tag,
> +                                                  st->codec->codec_tag);

the list is not 1:1 but n:n
one codec id can have multiple tags (ex: xvid/divx)
and one codec tag can have multiple ids (ex mpeg1/mpeg2)
you must check the values against the list

also dont forget to test your code against the regression tests & fate

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

Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
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