ffmpeg -i video_only.avi -vcodec copy -i audio_with_video.mp4 -vn -acodec libmp3lame  wr01.avi -map 0:0 -map 0:1
ffmpeg version N-39664-g6bfb304 Copyright (c) 2000-2012 the FFmpeg developers
  built on Apr  9 2012 20:29:24 with gcc 4.6.3
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-runtime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libass --enable-libcelt --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-libnut --enable-libope
njpeg --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libutvideo --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
  libavutil      51. 46.100 / 51. 46.100
  libavcodec     54. 14.101 / 54. 14.101
  libavformat    54.  3.100 / 54.  3.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 67.101 /  2. 67.101
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0. 10.100 /  0. 10.100
  libpostproc    52.  0.100 / 52.  0.100
[mpeg4 @ 01df9f20] Invalid and inefficient vfw-avi packed B frames detected
Input #0, avi, from '01.avi':
  Duration: 00:23:59.98, start: 0.000000, bitrate: 556 kb/s
    Stream #0:0: Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658), yuv420p, 852x480 [SAR 1:1 DAR 71:40], 23.98 tbr, 23.98 tbn, 23.98 tbc
Unknown decoder 'copy'