Opus is a modern high-efficiency audio codec that is especially suited to encode speech with very low bitrates.
Therefore, it’s a good fit to compress your Audiobook library so it consumes much less space.
First, choose a bitrate for Opus. I recommend to use 24kbit/s (24k) for general use, or 32 kbit/s (32k) if you want to have higher quality audio, e.g. if you are listening using good-quality headphones.
You can use ffmpeg directly by using this syntax:
ffmpeg -i <input file> -c:a libopus -b:a bitrate <output file>
but I recommend to use this shell function instead:
function audioToOpus { ffmpeg -i "$2" -c:a libopus -b:a "$1" "${2%.*}.opus" ; }Copy & paste it into your shell, then call it like this:
audioToOpus <bitrate> <input file>
Example:
audioToOpus 24k myaudiobook.mp3
This command will create myaudiobook.opus. myaudiobook.mp3 will not be deleted automatically.
In case you want to have this function available permanently, add the function definition to your ~/.bashrc or ~/.zshrc, depending on which shell you use.