[Ffmpeg-devel] [BUG] MPEG-4 artifacts, possibly demuxer-related

[Michael Niedermayer]

Hi

On Mon, Jan 30, 2006 at 03:07:33PM +0100, bond wrote:
> > On Mon, Jan 02, 2006 at 03:04:22PM +0100, Diego Biurrun wrote:
> > > Hey, I stumbled across another MPEG-4 file that shows artifacts:
> > >
> > >
> ftp://sandman.homedns.org/diego/ffmpeg/XviD_with_3_AAC-HE_audio_streams.avi
> > >
> > > I've tested with CVS MPlayer, CVS ffplay and MPlayer 1.0pre7try2.
> > > Interestingly xine CVS and vlc 0.8.4 play the file fine.  This indicates
> > > a demuxer problem, but it would be present in both the MPlayer and the
> > > libavformat demuxer.  The AVI file is an ODML AVI file.
> >
> > the file can be played correctly with lavf if you apply:
> >
> > @@ -303,6 +303,7 @@
> >                      if (st->codec->codec_id == CODEC_ID_XAN_WC4)
> >                          xan_video = 1;
> >                      st->need_parsing = 2; //only parse headers dont do
> slower repacketization, this is needed to get the pict type which is needed
> for generating correct pts
> > +                    st->need_parsing = 1;
> >  //                    url_fskip(pb, size - 5 * 4);
> >                      break;
> >                  case CODEC_TYPE_AUDIO:
> >
> > to avidec.c
> >
> > as far as i can see this AVI file has _many_ video frames in each chunk,
> sick
> > how can a person be capable of using a text editor (and writing software)
> and
> > at the same time be such a complete idiot writing a program generating so
> > broken avi files ...
> 
> packed bitstream as used by xvid and divx?

no that is supported and not that stupid, just an annoying hack to workaround
some limitations of some windows APIs
what this file has is more like 1 GOP per chunk though i didnt check if it
really is a GOP or if its randomly cut at about every 50 frames

[...]

-- 
Michael