HandBrake (Open Source)

HandBrake is an open-source, GPL-licensed, multiplatform, multithreaded video transcoder, available for MacOS X, Linux and Windows.

• Supported sources:

Any DVD-like source: VIDEO_TS folder, DVD image or real DVD (unencrypted--protection methods including CSS are not supported internally and must be handled externally with third-party software and libraries), and some .VOB and .TS files Most any multimedia file it can get libavformat to read and libavcodec to decode.

• Outputs:

File format: MP4, MKV, AVI or OGM Video: MPEG-4, H.264, or Theora (1 or 2 passes or constant quantizer/rate encoding) Audio: AAC, MP3, Vorbis or AC-3 pass-through (supports encoding of several audio tracks)

(source: http://handbrake.fr/?article=details)