[FFmpeg-user] Screencast produces only gray output

[look at ebookring.net]

I'm trying to get ffmpeg to do screencasting, that is- copy my computer
screen and the earthcam page video I'm watching.

The problem is that output file only shows a gray screen and nothing more.

Here's the code I'm using;

ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 20 -s 1280x800 -i :0.0 -acodec
pcm_s16le -vcodec libx264 -preset ultrafast -crf 0 -threads 0 output.mkv


Here's the FFmpeg version I'm using;

ffmpeg version N-42139-g7693543 Copyright (c) 2000-2012 the FFmpeg developers
  built on Nov  8 2012 22:15:12 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.  5.100 / 52.  5.100
  libavcodec     54. 71.100 / 54. 71.100
  libavformat    54. 36.100 / 54. 36.100
  libavdevice    54.  3.100 / 54.  3.100
  libavfilter     3. 21.106 /  3. 21.106
  libswscale      2.  1.102 /  2.  1.102
  libswresample   0. 16.100 /  0. 16.100
  libpostproc    52.  1.100 / 52.  1.100

I'm running this on Ubuntu 10.04




Any idea how to fix the problem?