Getting ready
Most Linux distributions include the ImageMagick tools. If your system does not include them, or if they are out of date, there are instructions for downloading and installing the latest tools on the ImageMagick website at www.imagemagick.org.
Like ImageMagick, many Linux distributions already include the ffmpeg and mencoder toolsets. The latest releases can be found at the ffmpeg and mencoder websites at http://www.ffmpeg.org and http://www.mplayerhq.hu.
Building and installing the video tools will probably require loading codecs and other ancillary files with confusing version dependencies. If you intend to use your Linux system for audio and video editing, it's simplest to use a Linux distribution that's designed for this, such as the Ubuntu Studio distributions.
Here are some recipes for a couple of common audio-video conversions: