The option -itsoffset does not actually offset the starting time of files, at
least as of February 13. See:
http://lists.mplayerhq.hu/pipermail/ffmpeg-user/2008-February/014044.html

I can confirm on my system.

chris@feathers:~$ ffmpeg -i /tmp/out.mp4 -sameq -itsoffset 00:00:05 -i
/tmp/out.mp3 /tmp/mixed.mp4
FFmpeg version SVN-r12158, Copyright (c) 2000-2008 Fabrice Bellard, et al.
  configuration: --enable-gpl --enable-x11grab --enable-pp --enable-pthreads
--enable-libfaac --enable-libfaad --enable-liba52 --enable-libx264
--enable-libdc1394 --enable-libgsm --enable-libmp3lame --enable-libxvid
--enable-libtheora --enable-libvorbis
  libavutil version: 49.6.0
  libavcodec version: 51.50.1
  libavformat version: 52.7.0
  libavdevice version: 52.0.0
  built on Feb 20 2008 12:40:31, gcc: 4.1.3 20070929 (prerelease) (Ubuntu
4.1.2-16ubuntu2)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/tmp/out.mp4':
  Duration: 00:00:11.6, start: 0.000000, bitrate: 164 kb/s
    Stream #0.0(und): Video: mpeg4, yuv420p, 640x480 [PAR 1:1 DAR 4:3], 10.00 tb(r)
Input #1, mp3, from '/tmp/out.mp3':
  Duration: 00:00:04.3, start: 0.000000, bitrate: 64 kb/s
    Stream #1.0: Audio: mp3, 44100 Hz, mono, 64 kb/s
File '/tmp/mixed.mp4' already exists. Overwrite ? [y/N] y
Output #0, mp4, to '/tmp/mixed.mp4':
    Stream #0.0(und): Video: mpeg4, yuv420p, 640x480 [PAR 1:1 DAR 4:3], q=2-31,
200 kb/s, 10.00 tb(c)
    Stream #0.1: Audio: libfaac, 44100 Hz, mono, 64 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #1.0 -> #0.1
Press [q] to stop encoding
frame=  116 fps=  0 q=0.0 Lsize=     271kB time=4.2 bitrate= 524.8kbits/s    
video:234kB audio:33kB global headers:0kB muxing overhead 1.280974%

The files can be found on ftp://upload.mplayerhq.hu/MPlayer/incoming/itsoffset/

reproduced.

clarification
has zero effect on mp4.
has a single useful effect with avi and mkv.
command type:
ffmpeg -i v.mp3 -itsoffset 20 -i input.avi -vcodec copy -acodec c
opy -y -map 1.0 -map 0.0 oo.avi

can place a positive (positive only) offset to video.
playback with directshow has the first frame as a still
for the duration of the offset.

with mplayer, with an avi, sound is played on it's own for the offset,
and then video kicks in.
with mkv there is no effect.

other combinations either do nothing or break audio video interleave.

i think it's mentioned somewhere that ffmpeg doesn't pad streams,
this would be a solution.
pad audio with silence,
pad video with the first frame 
for duration of offset.


ty
tripp

tripp wrote:
> tripp <ripon@dbzmail.com> added the comment:
> 
> reproduced.
> 
> clarification
> has zero effect on mp4.
> has a single useful effect with avi and mkv.
> command type:
> ffmpeg -i v.mp3 -itsoffset 20 -i input.avi -vcodec copy -acodec c
> opy -y -map 1.0 -map 0.0 oo.avi
> 
> can place a positive (positive only) offset to video.
> playback with directshow has the first frame as a still
> for the duration of the offset.

I don't think this is meant to be used like that, put -itsoffset before
-i, after all its means input ts offset, I may be wrong though.

[...]

you're right.
but it is before video input. where it 'works'
putting it before audio as well equals broken interleaving.

tripp

.

Same problem here.

Theoretically :
ffmpeg -i dvd.vob -itsoffset 10 -i dvd.vob -map 0.0 -map 1.1 ...
==
ffmpeg -i dvd.vob -itsoffset -10 -i dvd.vob -map 1.0 -map 0.1 ...

but only the second command works.

It seams that the video stream HAVE TO be taken from the second input file (the one 
on which itsoffset is applied) to make the command work.