[FFmpeg-devel] [PATCH] dvd audio sub-stream handling in the mpeg2 demuxer

[Michael Niedermayer]

On Tue, Feb 10, 2009 at 11:39:24AM +0530, Jai Menon wrote:
> On Tue, Feb 10, 2009 at 6:23 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> > On Mon, Feb 09, 2009 at 10:02:51AM +0530, Jai Menon wrote:
> >> Hi,
> >>
> >> Attached patch allows for demuxing of audio substreams stored as 0x06 type.
> >> Raw a/52 and subtitle detection is not included because of lack of a sample.
> >> Fixes issue 725 : MPEG2 PS with PCM audio
> >>
> >> --
> >> Regards,
> >>
> >> Jai
> >
> >> Index: libavformat/mpeg.c
> >> ===================================================================
> >> --- libavformat/mpeg.c        (revision 16998)
> >> +++ libavformat/mpeg.c        (working copy)
> >> @@ -450,6 +450,23 @@
> >>          } else if(es_type == STREAM_TYPE_AUDIO_AC3){
> >>              codec_id = CODEC_ID_AC3;
> >>              type = CODEC_TYPE_AUDIO;
> >> +        } else if(es_type == STREAM_TYPE_PRIVATE_DATA){
> >> +            uint8_t audio_id;
> >> +
> >> +            // probe for dvd audio sub-stream
> >> +            type = CODEC_TYPE_AUDIO;
> >> +            audio_id = get_byte(s->pb);
> >> +            url_fseek(s->pb, -1, SEEK_CUR);
> >> +            switch(audio_id & 0xe0) {
> >> +                case 0xa0:  codec_id = CODEC_ID_PCM_DVD;
> >> +                            break;
> >> +                case 0x80:  if((audio_id & 0xf8) == 0x88)
> >> +                                 codec_id = CODEC_ID_DTS;
> >> +                            else codec_id = CODEC_ID_AC3;
> >> +                            break;
> >> +                default:    av_log(s, AV_LOG_ERROR, "Unknown 0x1bd sub-stream\n");
> >> +                            goto skip;
> >> +            }
> >>          } else {
> >>              goto skip;
> >>          }
> >> @@ -508,7 +525,17 @@
> >>   found:
> >>      if(st->discard >= AVDISCARD_ALL)
> >>          goto skip;
> >> -    if (startcode >= 0xa0 && startcode <= 0xaf) {
> >> +
> >> +    if(startcode == 0x1bd) {
> >> +        // skip dvd audio sub-stream header
> >> +        url_fskip(s->pb, 4);
> >> +        len -= 4;
> >> +    }
> >> +
> >> +    if ((startcode >= 0xa0 && startcode <= 0xaf) ||
> >> +        ((startcode == 0x1bd) &&
> >> +        ((st->codec->codec_id == CODEC_ID_PCM_S16BE) ||
> >> +         (st->codec->codec_id == CODEC_ID_PCM_DVD)))) {
> >>          int b1, freq;
> >>
> >>          /* for LPCM, we just skip the header and consider it is raw
> >
> > what about:
> >     }
> >
> >     es_type = m->psm_es_type[startcode & 0xff];
> > -    if(es_type > 0){
> > +    if(es_type > 0 && es_type != STREAM_TYPE_PRIVATE_DATA){
> >         if(es_type == STREAM_TYPE_VIDEO_MPEG1){
> >             codec_id = CODEC_ID_MPEG2VIDEO;
> >             type = CODEC_TYPE_VIDEO;
> > ...
> >
> > and then have the detection under if(startcode == 0x1bd)
> > this seems more robust but maybe iam missing something?
> 
> yes thats better, i was just trying hard not to change the structure
> of the existing code.
> 
> > also id read the 4 byte header before
> >  /* now find stream */
> >    for(i=0;i<s->nb_streams;i++) {
> >        st = s->streams[i];
> >        if (st->id == startcode)
> >            goto found;
> >    }
> > that would avoid the seek back and "skip dvd audio sub-stream header"
> 
> reworked and revised patch attached.

looks ok assuming mans has no sugestions for improvment

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

Opposition brings concord. Out of discord comes the fairest harmony.
-- Heraclitus
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