[FFmpeg-devel] Problem with seeking in avi file.

[Michael Niedermayer]

Hi

On Sat, Aug 11, 2007 at 10:45:45AM +1000, Neil Brown wrote:
> 
> I have another interesting movie file that ffmpeg doesn't quite work
> properly with.
> 
> This one is an avi file containing dvvideo extracted off a digital
> camcorder (I can find out what program was used to exact it if that
> might be of interest).
> 
> Anyway, the problem is that the first time that I seek into the file,
> if I aim for beyond 4:57, I alway arrive at 4:57.  Subsequent seeks
> work as expected.
> e.g.
> 
>   ffmpeg -ss 400 filename.avi
> 
> starts at 4:57, as does any number of seconds greater than 300.\
> 
> The file starts with RIFF with a size of 1069618820.
> This covers about 1/4 of the file (5 minutes of about 20).
> There are 3 more RIFF headers of 1069611496, then
> one of 63795560 which completes the file.
> 
> The file contains a 'dmlh' tag, so is_odml is set.
> The file contains a 'LIST' tag with a 'movi' subtag and a size of
> 1069467476.  This just covers the first of 5 RIFF sections.
> 
> So ->movi_end gets set to 1/4 of the way through the file - the end of
> the first section.
> 
> In avi_read_packet, after a seek further into the file,
> 'i' is the current position in the file, so this code:
> 
>         if (i >= avi->movi_end) {
>             if (avi->is_odml) {
>                 url_fskip(pb, avi->riff_end - i);
>                 avi->riff_end = avi->movi_end = url_fsize(pb);
>             } else
>                 break;
>         }
> 
> seeks back to the end of the first RIFF, then sets movi_end to the
> correct end of the file.
> It seems to me that if 'odml' allows as to set movi_end to fsize at
> this point, it should allow movi_end to be set to fsize right at the
> start.

yes, setting it to fsize is wrong no matter where its done, it breaks
avi_load_index()
the code quoted above should be removed its broken
you seem pretty good at spotting totally broken code :)
ill try to fix this one ...

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Concerning the gods, I have no means of knowing whether they exist or not
or of what sort they may be, because of the obscurity of the subject, and
the brevity of human life -- Protagoras
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