ffmpeg:

For example, from m4a to ogg, on the command line:

ffmpeg -i input.m4a -vn -sn -acodec libvorbis output.ogg

Where:

  • -vn to exclude video
  • -sn to exclude subtitles
  • -i to indicate the input
  • -acodec to say that you are going to use an audio codec
  • libvorbis for ogg

The order of the arguments is important.