Support ogg audio files on Safari via:

[mayeaux]

https://github.com/brion/ogv.js/

[mayeaux]

Actually, the proper way will be to convert everything to .mp3

If people want native .ogg support they can do a PR with a flag to support alt formats, and then use ogv on the frontend for Safari

[BassOfBass]

But <audio> supports several <source> elements and the agent picks the one the value of type attribute it can understand, otherwise sends the request to server for each <source> until it gets the one it can understand. It does increase the storage sizes, but reduces the round trips to server and makes compatibility a lot less painful, especially since there is a way to provide a fallback in the form of direct link to the file anyway.
Will require a lot of rework, though.
For one, Upload.js has to be rewritten to accommodate to the array of sources (and tracks), and some details present on the model itself have to be moved in there. So it requires writing a separate migration script too.
After that rewriting media.pug will be a piece of cake.