Video Format Conversion
Find video information
$ mplayer -vo null -ao null -identify -frames 0
Convert file types
This is real simple and only needs one line.
$ ffmpeg -i filename.ext -ab 56 -ar 22050 -b 500 -s 320x240 filename.ext
The two .ext extensions should obviously be different. Also, the new size -s could be whatever you want.
To keep the size the same but just convert.
ffmpeg -i InputFile.mpg -ab 128 -b 1200 -vcodec mpeg4 OutputFile.mp4