Ogg

Ogg is free professional-grade media format endorsed by FSF. Ogg Vorbis encodes audio and Ogg Theora encodes video. When you see a file with the Ogg extension play it!

Run

ffmpeg -i input.mp3 output.ogg
ffmpeg -i input.mkv -q:a 10 -q:v 10 output.ogg

Ogg