Something

ffmpeg -i _cat.mp4 -acodec copy -vcodec copy _final.mp4
FFmpeg version SVN-r7319, Copyright (c) 2000-2006 Fabrice Bellard, et al.
  configuration:  --enable-gpl --enable-pp --enable-mp3lame --enable-xvid --enable-a52 --enable-libogg --enable-vorbis --enable-x264 --enable-faad --enable-faac --enable-libgsm --enable-dts --extra-cflags=-DHAVE_LRINTF 
  libavutil version: 49.1.0
  libavcodec version: 51.26.0
  libavformat version: 51.6.0
  built on Dec 14 2006 20:57:52, gcc: 4.1.2 20061115 (prerelease) (SUSE Linux)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '_cat.mp4':
  Duration: 00:03:02.9, start: 0.000000, bitrate: 807 kb/s
  Stream #0.0(und): Video: h264, yuv420p, 320x240, 25.00 fps(r)
  Stream #0.1(und): Audio: aac, 44100 Hz, stereo
Output #0, mp4, to '_final.mp4':
  Stream #0.0: Video: h264, yuv420p, 320x240, q=2-31, 25.00 fps(c)
  Stream #0.1: Audio: aac, 44100 Hz, stereo
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1
[mp4 @ 0x84ae40]track 1: codec frame size is not set
Could not write header for output file #0 (incorrect codec parameters ?)