[Ffmpeg-devel] [Bad news]: MPEG Seek has failed to work in FFmpeg SVN

[Michael Niedermayer]

Hi

On Fri, Nov 03, 2006 at 06:02:34PM +0100, Steve Lhomme wrote:
> M?ns Rullg?rd wrote:
> >Steve Lhomme said:
> >>
> >>M?ns Rullg?rd wrote:
> >>>Steve Lhomme said:
> >>>>QuickTime wrote:
> >>>>>Dear:
> >>>>Hi Quicktime,
> >>>>
> >>>>>FFmpeg fails to decode video(avcodec_decode_video() never return
> >>>>>picture) after perform SEEK on mpeg file format
> >>>>>
> >>>>>It seems that the seek&decode abiliity for mpeg files have been broken
> >>>>>for 2 months(ealier than August )
> >>>>>
> >>>>>ffmpeg  -ss 00:00:10 -i test.mpg  -r 25 test.mp4
> >>>>>.....
> >>>>>Input #0, mpeg, from 'test.mpg':
> >>>>> Duration: 00:00:24.0, start: 0.346711, bitrate: 2314 kb/s
> >>>>> Stream #0.0[0x1e0]: Video: mpeg1video, yuv420p, 352x288, 2000 kb/s,
> >>>>>25.00 fps(r)
> >>>>> Stream #0.1[0x1c0]: Audio: mp2, 44100 Hz, stereo, 192 kb/s
> >>>>>Output #0, mp4, to 'test.mp4':
> >>>>> Stream #0.0: Video: mpeg4, yuv420p, 352x288, q=2-31, 200 kb/s, 25.00
> >>>>>fps(c)
> >>>>> Stream #0.1: Audio: aac, 44100 Hz, stereo, 64 kb/s
> >>>>>Stream mapping:
> >>>>> Stream #0.0 -> #0.0
> >>>>> Stream #0.1 -> #0.1
> >>>>>frame=    0 q=0.0 Lsize=     120kB time=14.8 bitrate=  66.1kbits/s
> >>>>>video:0kB audio:114kB global headers:0kB muxing overhead 4.833664%
> >>>>>.....
> >>>>I've had similar problems (actually crashes) with some MPEG2 samples
> >>>>(from DVDs) for a long time. Maybe if you can provide a sample and say
> >>>>what platform you use, it could help.
> >>>Yeah, if Steve hadn't refused to provide samples, maybe this had been 
> >>>fixed
> >>>already.
> >>Look at the message "Re: [Ffmpeg-devel] MPEG2 decoding problems" from
> >>2006-03-02 there is a chems1.vob sample. The URL should still work.
> >
> >I have a copy of the file.
> >
> >>It was not fixed because you need to seek at a specific place in the
> >>file to crash. Maybe you can manage to do that by doing a
> >>forward/backward seek in ffplay during a specific fraction of second
> >>during playback. I proposed to modify ffplay to test it but it was
> >>rejected...
> >
> >We do not support modified versions of ffmpeg.  If this is really a bug in
> >our code (and caused by your mods), it should be possible to trigger it by
> >cutting that file of yours in the right spot.  Find this spot, and we'll
> >look into it.  You can't expect us to do all the work.
> 
> I tried it. Unfortunately it not as simple as you write it. Our code 
> uses AVSEEK_FLAG_BYTE when seeking in VOB files (since the timestamps 
> may not be contiguous/accurate throughout the file). And neither 
> ffmpeg.c nor ffplay.c use this flag to seek.

why dont you add AVSEEK_FLAG_BYTE support to ffmpeg/ffplay? maybe with
a AVFMT_DISCONTINUOS_AKA_USELESS_TIMESTAMPS in AVOutputFormat.flags which
selects that then by default for such formats

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
Today you'd get arrested for mere telling someone where the library is