[FFmpeg-user] ffmpeg: How can this output be corrected?

[maujhsn]

maujhsn209 at maujhsn209-desktop:~$ ffmpeg -f alsa -ac 2 -ar 44100 -i alsa -f
x11grab -r 30 -s 1024x768 -i :0.0-c:a pcm_s16le -c:v libx264 -preset
ultrafast -crf 0 -threads 0 output.mkv
ffmpeg version git-2013-01-06-c44b4ee Copyright (c) 2000-2013 the FFmpeg
developers
  built on Jan  6 2013 00:21:35 with gcc 4.4.3 (Ubuntu 4.4.3-4ubuntu5.1)
  configuration: --enable-gpl --enable-libfaac --enable-libmp3lame
--enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora
--enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree
--enable-version3 --enable-x11grab
  libavutil      52. 13.100 / 52. 13.100
  libavcodec     54. 85.101 / 54. 85.101
  libavformat    54. 59.105 / 54. 59.105
  libavdevice    54.  3.102 / 54.  3.102
  libavfilter     3. 32.100 /  3. 32.100
  libswscale      2.  1.103 /  2.  1.103
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
ALSA lib pcm.c:2211:(snd_pcm_open_noupdate) Unknown PCM alsa
[alsa @ 0xaa18c20] cannot open audio device alsa (No such file or directory)
alsa: Input/output error