Support more bit depths

[200sc]

Right now we support 16-bit audio. It is trivial but a good amount of work to extend what we have to support other bit depths. Some research into what bit depths would be meaningful would help, and if there's some conflict between, say, float64 and int64 encoding styles that we need more information for.

Along the way we should look into if there's a better way to resolve filters on audio of different bit depths than just using a switch.