Re: [mediacapture-main] How is adaptive frame rate to be handled?

That makes a lot of sense, but when I think about it doesn't seem very
 stable or deterministic.

> if opening a variable-rate camera in a dark room with frameRate: { 
min: 30 }, this will cause an instant overconstrained event - but 
that's what you asked for, so you should get it.

OK, but I didn't get what I wanted at all, and what would I do next? 
If I ask for `frameRate: { min: 30 }` again, wont the same thing 
happen? Or should the UA remember that that didn't work the last time 
and try other modes instead (even if the lighting conditions may have 
improved, which it cannot know)? Am I to experiment with lower widths 
and heights? This seems imprecise and unproductive.

The camera may have other lower resolution modes that actually *could*
 do a minimum of 30 frames all the time, even in low light, but they 
may be over-shadowed by this adaptive mode that's *overselling* its 
capabilities and therefore receives an overly-optimistic fitness 
distance. If I used high ideal-values for width and height, which is 
likely, then the lower resolutions wont stand a chance.

(If there are multiple cameras, I may also have bothered the user for 
the wrong one, and potentially have to bother them again, though I'm 
the first to admit that picking cameras based on frame rate is silly).

I think we have to try the opposite, to **undersell** capabilities. 
E.g. `frameRate: { min: 30 }` would *only* be satisfied by cameras 
that can sustain 30 fps all the time, regardless of lighting 
conditions, and not our OP camera.

To reach our OP camera I would have to use `frameRate: { min: 10, 
ideal: 30, max: 30 }`. Coupled with high ideal-values for width and 
height, that should give me the right one.

This is may seem extremely conservative, but it's more deterministic, 
and doesn't have the problem of good modes being overshadowed by modes
 that under-deliver, or the problem of `overconstrained` firing in 
response to lighting changes.

-- 
GitHub Notif of comment by jan-ivar
See 
https://github.com/w3c/mediacapture-main/issues/193#issuecomment-118222161

Received on Friday, 3 July 2015 03:34:12 UTC