Agree with bobtomay. I recently purchased iFFmpeg (for a measly $12) because it was the only video converter program that would properly re-encode JUST the audio on some video files I wanted to put on my iPad. It does a nice job with whatever I give it, but yes, depending on your needs MPEG Streamclip (free) or Handbrake (free, needs VLC which is also free), or Video Monkey (free) or Miro Video Converter (free) may do the job for you. I also like the look of Permute ($10), which does batch encoding with a beautifully minimalist interface.