# ffmpeg -i test.mkv -acodec copy -vcodec copy -y test.mp4


FFmpeg version SVN-rUNKNOWN, Copyright (c) 2000-2007 Fabrice Bellard, et al.
  configuration: --enable-gpl --enable-pp --enable-swscaler --enable-pthreads --enable-libvorbis --enable-libtheora --enable-libogg --enable-libgsm --enable-dc1394 --disable-debug --enable-libmp3lame --enable-libfaadbin --enable-libfaad --enable-libfaac --enable-xvid --enable-x264 --enable-liba52 --enable-amr_nb --enable-amr_wb --enable-shared --prefix=/usr
  libavutil version: 1d.49.3.0
  libavcodec version: 1d.51.38.0
  libavformat version: 1d.51.10.0
  built on Mar 17 2009 21:11:10, gcc: 4.2.4 (Ubuntu 4.2.4-1ubuntu3)
[matroska @ 0x7fa20aa0f160]Ignoring seekhead entry for ID=0x1549a966
[matroska @ 0x7fa20aa0f160]Ignoring seekhead entry for ID=0x1654ae6b
[matroska @ 0x7fa20aa0f160]Ignoring seekhead entry for ID=0x114d9b74
[matroska @ 0x7fa20aa0f160]Unknown entry 0x73a4 in info header
[matroska @ 0x7fa20aa0f160]Unknown track header entry 0x55aa - ignoring
[matroska @ 0x7fa20aa0f160]Unknown track header entry 0x23314f - ignoring
[matroska @ 0x7fa20aa0f160]Unknown track header entry 0x55ee - ignoring
[matroska @ 0x7fa20aa0f160]Unknown track header entry 0xaa - ignoring
[matroska @ 0x7fa20aa0f160]Unknown track header entry 0x55aa - ignoring
[matroska @ 0x7fa20aa0f160]Unknown track header entry 0x23314f - ignoring
[matroska @ 0x7fa20aa0f160]Unknown track header entry 0x55ee - ignoring
[matroska @ 0x7fa20aa0f160]Unknown track header entry 0xaa - ignoring
Input #0, matroska, from 'test.mkv':
  Duration: 00:41:49.8, bitrate: N/A
  Stream #0.0: Audio: ac3, 48000 Hz, 5:1
  Stream #0.1: Video: h264, yuv420p, 1280x720, 23.98 fps(r)
Output #0, mp4, to 'test.mp4':
  Stream #0.0: Video: h264, yuv420p, 1280x720, q=2-31, 1000.00 fps(c)
  Stream #0.1: Audio: ac3, 48000 Hz, 5:1
Stream mapping:
  Stream #0.1 -> #0.0
  Stream #0.0 -> #0.1
[mp4 @ 0x7fa20aa0f160]track 1: codec frame size is not set
Could not write header for output file #0 (incorrect codec parameters ?)