[:http://sourceforge.net/projects/ffmpeg/|ffmpeg] is a very useful tool for conversion between various video encodings.
If you build it with all the supported libraries, you can convert almost all kinds of video files to the desired encoding.

Recently a video that we recorded was handed over to me in VCD format (!). Feisty doesn't seem to like VCDs much:

Opening audio decoder: [libdv] Raw DV Audio Decoder
Unknown/missing audio format -> no sound
ADecoder init failed
Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders
Cannot find codec 'dvaudio' in libavcodec...
ADecoder init failed
ADecoder init failed


The option left was to rip the VCD:

vcdxrip --cdrom-device=/dev/hdb --rip