ffmpeg screencast

ubuntu@ubuntu:~$ ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 30 -s 1024x720 -i :0.0 -qscale 1 -acodec pcm_s161e  -vcodec libx264 -vpre lossless_ultrafast -threads 0 output.mkv
FFmpeg version SVN-r0.5.1-4:0.5.1-1ubuntu1.3, Copyright (c) 2000-2009 Fabrice Bellard, et al.
  configuration: --extra-version=4:0.5.1-1ubuntu1.3 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --disable-stripping --disable-vhook --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
  libavutil     49.15. 0 / 49.15. 0
  libavcodec    52.20. 1 / 52.20. 1
  libavformat   52.31. 0 / 52.31. 0
  libavdevice   52. 1. 0 / 52. 1. 0
  libavfilter    0. 4. 0 /  0. 4. 0
  libswscale     0. 7. 1 /  0. 7. 1
  libpostproc   51. 2. 0 / 51. 2. 0
  built on Dec 21 2011 18:41:38, gcc: 4.4.3
[alsa @ 0x2141260]capture with some ALSA plugins, especially dsnoop, may hang.
Input #0, alsa, from 'pulse':
  Duration: N/A, start: 1327562896.989502, bitrate: N/A
    Stream #0.0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
[x11grab @ 0x215d480]device: :0.0 -> display: :0.0 x: 0 y: 0 width: 1024 height: 720
[x11grab @ 0x215d480]shared memory extension  found
Input #1, x11grab, from ':0.0':
  Duration: N/A, start: 1327144604.298973, bitrate: 707788 kb/s
    Stream #1.0: Video: rawvideo, rgb32, 1024x720, 707788 kb/s, 30 tbr, 1000k tbn, 30 tbc
Unknown encoder 'libx264'