ffmpeg

    Previously named libav a like audio, v like video

    Require package ffmpeg (previously libav-tools)

    Codec of file

    avprobe file.mp4
    

    Note: could use ohter file like .flv, .avi, ...

    Supported formats

    ffmpeg -formats
    

    Supported codecs

    ffmpeg -codecs
    

    Note: To have more codec, check libavcodec-extra-...

    Example

    ffmpeg -i input.flv -acodec aac -vcodec h264 -o output.mp4
    

    Tips

    Reduce the size of a video

    avconv -i input.mp4 -c:v libx264 -crf 28 -c:a copy output.mp4
    

    source