Client Resolution Thresholds

Creating a thread here for tracking.

In the latest unstable, setting the minHeightForQualityLvl property does not appear to have an impact when the bridge kicks in. With 2 participants, the constraints are respected, but once a 3rd participant enters the meeting, it appears the property is ignored.

I haven’t tested this in the latest stable to confirm if the issue exists there, though.

@jallamsetty FYI

I lowered the threshold for requesting HD resolution. When I do a 2-participant call, I get 720p as expected with tile height at 360p:

However, once a 3rd participant joins, the constraint is ignored and resolution falls to standard (at the same tile height):

Please see the explanation here - Poor Video Quality Latest Jitsi Update (5142-1) - #20 by jallamsetty

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Thank you, @jallamsetty! That makes complete sense.

In an unrelated but related question :smile:, is there any potential danger to lowering the maxBitratesVideo value? I mean, if I can constrain my setup to use just 200kbps for HD for instance (not sure that’s possible), why wouldn’t I prefer that? Or is there an absolute minimum number required for each resolution type? I have observed that on VP8, these are the typical bitrates:

180p [LD] - 200kbs
360p [SD] - 500kbps
720p [HD] - 2500kbps

So let’s say I set the maxBitratesVideo value for HD to be 500kbps, for instance, what are the potential issues? Will I in fact get HD quality stream at 500kbps or will it just spit SD quality with an HD label?

If you decrease the maxBitrates below a certain threshold (for a given resolution), the video quality will suffer. The resolution might still be HD but the quality will suffer, the video will appear pixelated and the frame rate could be dropped.
These are the bitrates we have on meet.jit.si for VP8
videoQuality: {
maxBitratesVideo: {
low: 200000,
standard: 500000,
high: 1500000
},

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Thank you. Again, makes complete sense. I appreciate the time you took to explain.