Convert audio to OGG format via Terminal

Ogg is a container format. It typically uses the Vorbis audio codec. You can download a static build of ffmpeg and use the bundled libvorbis encoder:

ffmpeg -i input.wav -c:a libvorbis -qscale:a 5 output.ogg

According to the Vorbis encoding guide, the quality range is from 0–10, where 10 is the highest quality and 3–6 are a good range to try. In the above example we used 5 as quality.

I've come across this question a couple of times, this is what worked for me:

$ ffmpeg -y -i foo.mp3  -strict -2 -acodec vorbis -ac 2 -aq 50 foo.ogg

Source: http://infoheap.com/ffmpeg-convert-mp3-to-ogg-on-mac/