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

[Jai Menon]

On Tue, Feb 10, 2009 at 5:03 PM, M?ns Rullg?rd <mans at mansr.com> wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
>
>> 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
>
> No immediate ideas here.  The entire stream type detection code could
> use a cleanup, but that's not Jai's job.

If you have any specific ideas, I could take a shot. Other than that,
we'll have
to wait for the next sample which doesn't work ;) (hopefully none).

-- 
Regards,

Jai