robert@robert-Aspire-5349:~$ ffmpeg -f alsa -ac 2 -i hw:1 -r 30 -s 1366x768 -f x11grab -i :0.0 -vcodec msmpeg4v2 -qscale 2 screencast.avi
ffmpeg version git-2012-04-28-f1b8209 Copyright (c) 2000-2012 the FFmpeg developers
  built on Apr 28 2012 13:11:31 with gcc 4.6.3
  configuration: --enable-gpl --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libx264 --enable-nonfree --enable-postproc --enable-version3 --enable-x11grab
  libavutil      51. 48.100 / 51. 48.100
  libavcodec     54. 16.100 / 54. 16.100
  libavformat    54.  3.100 / 54.  3.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 72.100 /  2. 72.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0. 11.100 /  0. 11.100
  libpostproc    52.  0.100 / 52.  0.100
[alsa @ 0x1e1e120] cannot set channel count to 2 (Invalid argument)
hw:1: Input/output error
robert@robert-Aspire-5349:~$