FFmpeg - command line video and audio converter
Usage examples:
-To get a list of available formats, codecs (media format) and filters.
ffmpeg -formats
ffmpeg -codecs
ffmpeg -filters
-Print information about the in input media file.
ffmpeg -i media.mkv
-For extracting audio from a video:
ffmpeg -i input-media.ogv -vn -acodec copy output-audio.oga