http://handbrake.fr/index.php




Details

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

Screenshots
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 and MKV
    * Video: MPEG-4, H.264, or Theora
    * Audio: AAC, CoreAudio AAC (OS X Only), MP3, or Vorbis. AC-3 pass-through, DTS pass-thorugh (MKV only)

Misc features:

    * Chapter selection
    * Subtitles
    * Integrated bitrate calculator
    * Picture deinterlacing, cropping and scaling
    * Live Video Preivew

Credits

HandBrake uses a lot of (L)GPL librairies from the Linux world: 

                          Thank their authors!