[Moq] Top Tracks and SSTS (or ABR in general)

[Ian Swett <[e-mail]>]

I reviewed the most recent Top Tracks PR, and I continue to wonder exactly
how it will work with SSTS (or another ABR algorithm).

At a high level, I believe I know what one might want, but the mechanisms
to achieve it are unclear to me.

I realize there are use cases for Top Tracks without ABR, but for the VC
usecase, ABR seems essential?

Specific questions:
1) How do you send the correct SUBSCRIBE_TRACKS initially? Do you use a
Track Property Filter to filter for the ideal resolution, and combine that
with Top Tracks?
2) How do you ensure the focal viewport gets higher priority when deciding
which video feed to downswitch?
3) If a client pins a video feed other than the VC's default, how does
prioritization work?
4) Are there any demos of Top Tracks and SSTS working together, even if
it's a simulation and not the public internet?

I asked the Meet team to describe what they do today. That may or may not
be proprietary, but it doesn't matter because it's sufficiently complex
that I can't summarize it anyway. I'm sure it's complex for very good
reasons, but it doesn't give me confidence we'll design a comparable
solution in MoQ soon.

Ian