Linux has a wonderful tool called ffmpeg that makes video conversion easy....as long as you're OK with the command line.
Here is a sample command line argument that would help you convert to the FLV format:
ffmpeg -i input.mp4 -ar 22050 -ab 32 -f flv output.flv
Let's explain some of the operators in this command:
- "-i" indicates that the next word is the input file name (input.mp4)
- "-ar 22050" indicates an audio sampling rate of 22050 Hz
- "-ab 32" indicates that the audio bitrate is 32kbits/second
- "-f flv" indicates that we wish to convert the video to the FLV format
- You could also force the video to convert to a particular resultion with "-s 320x240"