In newer Ubuntu releases the Opus codec is included in the libavcodec libraries that will be installed with ffmpeg. Audio encoding is then done with

ffmpeg -i infile.ext <options> outfile.opus

The audio converter shipped with the opus-tools can convert audio in raw, wave or AIFF format. The minimal syntax uses default settings:

opusenc input.wav output.opus

We may want to add a better bitrate as the default 96 kbps with the option --bitrate N.nnn (for all options consult the manpage for opusenc).

To convert mp3 "on the fly". i.e. without creating a temporary file we can pipe the output from ffmpeg to opusenc like this:

ffmpeg -i input.mp3 -f wav - | opusenc --bitrate 256 - output.opus