So I am a bit of a casual codec geek, and I keep thinking that if #mastodon expands its post type to include other media, such as audio, it would be best storing it all encoded in #opus.
Firstly the space this would save would be a great help to non commercial instance hosts.
But secondly it would keep everything open source.
I can see this being an issue with iPhone users, but the decoder can be packaged into their client app.