hi all

we're using ffmpeg to convert 3gp videos taken from phones to mp4s and wmv's
we're having a problem with the output videos playing faster than the original

eg. the 3gp video goes for 4 seconds
but the mp4 file goes for 3 seconds

all the footage is there, it just plays faster

if it helps, here is the command line
ffmpeg -i $srcFile -s qcif -b 96 -ar 8000 -ab 16 -vcodec mpeg4 $destFile

i will add the output string in a couple of minutes

Code:
Input #0, mov,mp4,m4a,3gp, from '/videos/srcfile.3gp':
  Duration: 00:02:54.5, start: 0.000000, bitrate: 3 kb/s
  Stream #0.0: Video: h263, 176x144, 12.60 fps
  Stream #0.1: Audio: amr_nb, 8000 Hz, mono
Output #0, mp4, to '/videos/destFile.mp4':
  Stream #0.0: Video: mpeg4, 176x144, 12.60 fps, q=2-31, 96 kb/s
  Stream #0.1: Audio: aac, 8000 Hz, mono, 16 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1
Press [q] to stop encoding
frame=   48 q=0.0 Lsize=      97kB time=3.8 bitrate= 208.4kbits/s
video:77kB audio:17kB global headers:0kB muxing overhead 2.132194%
has anyone experienced something like this before using ffmpeg or other programs (on linux or windows)?
i'm using an ffmpeg rpm downloaded from dag.wieers.net
which i recompiled to add amr_nb support for 3gp audio decoding

i've worked out that the audio stream is at the right speed
but the video stream finishes well before

thanks
dave