The simple example will show you all you need to know. Handles all those crazy command-line options for ya, nice.
# MDM Adding the following for all this video editing (from DVD's, camcorder).... [a52 v4l2 nuv x264]
# MDM Definitely want to rip DVD's as needed [css]; use alsa (not [oss]) media-video/cinelerra-cvs css -oss
After emerging avidemux, I needed to do a revdep-rebuild to fix libfaad.so for transcode, ffmpeg, etc. I did a full [emerge_all], aifol.