When I tried to convert a video file, i got this message (using the generated command line):
Unknown encoder 'libx264'
Being a newbie, I searched for solution using google and I found this: http://ubuntuforums.org/showthread.php?t=1117283
I followed the instuction in chapter B. and everthing was fine.
If you are using Statler you'll want to make sure that you have the debian-multimedia repos enabled, this will allow you to install the various grstreamer packages with all of the codecs you'll ever need :-)
Here is what I have installed:
gstreamer0.10-alsa gstreamer0.10-ffmpeg gstreamer0.10-fluendo-mp3 gstreamer0.10-lame gstreamer0.10-nice gstreamer0.10-plugins-bad gstreamer0.10-plugins-base gstreamer0.10-plugins-good gstreamer0.10-plugins-really-bad gstreamer0.10-plugins-ugly gstreamer0.10-x gstreamer0.10-x264
Enabling the proper repos are easy too, just go to http://debian-multimedia.org/ !
Arch Linux 2010.05 (x64)