[audio category] Interactions with content-hint spec

Filing this issue on behalf of HTA from Google from a side thread to have the discussion here:

Please check out the existing extension "contentHint".
https://w3c.github.io/mst-content-hint/
It seems to be in the same area of application, and is already deployed in Chrome (with effects appliedfor the video case).

On reading your proposal, it seems that the additional feature you want in addition to what content-hint provides is the ability to select sources based on the kind of output they have. I'm not sure whether that makes sense; it fits with the way constraints are used to control echo cancellation and noise suppression, but that's perhaps not an important consideration.

Category selection note: "speech" for human understanding and "speech" for machine recognition may well be two different categories - it's likely that speech recognition will want to do bandpass filtering in the algorithm rather than having the audio processor do it for them, for instance. My intuition is that "unprocessed" is what most speech recognition folks want. (They also dont care much about delay, which is very important in interactive audio. But that's an orthogonal parameter.)