ffmpeg screencast

:~$ ffmpeg -f x11grab -r 25 -s 1024x768 -i :0.0+100,200 -f alsa -ac 2 -i pulse output.flv
ffmpeg version git-2012-12-22-44fe118 Copyright (c) 2000-2012 the FFmpeg developers
  built on Dec 21 2012 17:28:32 with gcc 4.7 (Ubuntu/Linaro 4.7.2-2ubuntu1)
  configuration: --enable-gpl --enable-libass --enable-libfaac --enable-libfdk-aac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-librtmp --enable-libtheora --enable-libvorbis --enable-libvpx --enable-x11grab --enable-libx264 --enable-nonfree --enable-version3
  libavutil      52. 12.100 / 52. 12.100
  libavcodec     54. 81.100 / 54. 81.100
  libavformat    54. 49.102 / 54. 49.102
  libavdevice    54.  3.102 / 54.  3.102
  libavfilter     3. 29.100 /  3. 29.100
  libswscale      2.  1.103 /  2.  1.103
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
[x11grab @ 0xaa7b860] device: :0.0+100,200 -> display: :0.0 x: 100 y: 200 width: 1024 height: 768
[x11grab @ 0xaa7b860] shared memory extension found
X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  130 (MIT-SHM)
  Minor opcode of failed request:  4 (X_ShmGetImage)
  Serial number of failed request:  11
  Current serial number in output stream:  11