Use cases that don't require insertion into pipeline

One requirement for many use cases is that it support inserting process
into the media pipeline.
This leads to requirements for pretty hard realtime processing (20 ms
being a long time), and thus to having to make APIs that make sense in
workers or separate threads (like AudioProcessingWorklet).


Some use cases don't require that - they're perfectly workable for stuff
that only needs listening in on the media.

For instance:

- Echo detectors used to create a "Fix your configuration" message
rather than trying to remove the echo

- Speech recognizers that associate certain voices with certain persons
- may be used to show the name of the person speaking; this won't need
to be realtime, having the name show up 0.5 seconds after the person
starts speaking isn't a big deal

- Video quality monitors that look at encoded frames to figure out what
QP values were used, and displays a "low quality because sender thinks
you have low bandwidth" type of message

I think these use cases can be significant, and can be unlocked with
APIs that don't demand as much in new spec & implementation than the
more ambitious "in-pipeline" use cases.


Harald, typing until the "aha" moment goes away