I am looking for some way to play audio streams while displaying metadata in the video stream.
That’s not something Channels can or will do.
I’d suggest a shoutcast compatible audio player that knows what to do with streaming radio stations.
I was thinking about generating the video part via ffmpeg
Then that's just a Custom Channel. In that case, you can do whatever you want as long as Channels is provided a stream of video it can play back.
So the request is to the community, not for the ability natively to Channels. Got it!
Here is a nice find - Get Started | Volumio