Bitrate based quality tracking for DownTrack #1491
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With score normalization, the quality indicator showed good
under conditions which should have normally showed some badness.
So, a few things in this PR
- Do not normalize scores
- Pick the weakest link as the representative score (moving away from
averaging)
- For down track direction, when reporting delta stats, take the number
of packets sent actually. If there are holes in the feed (upstream
packet loss), down tracks should not be penalised for that loss.
State of things in connection quality feature
- Audio uses rtcscore-go (with a change to accommodate RED codec). This
follows the E-model.
- Camera uses rtcscore-go. No change here. NOTE: THe rtscore here is
purely based on bits per pixel per frame (bpf). This has the following
existing issues (no change, these were already there)
o Does not take packet loss, jitter, rtt into account
o Expected frame rate is not available. So, measured frame rate is
used as expected frame rate also. If expected frame rate were available,
the score could be reduced for lower frame rates.
- Screen share tracks: No change. This uses the very old simple loss
based thresholding for scoring. As the bit rate varies a lot based on
content and rtcscore video algorithm used for camera relies on
bits per pixel per frame, this could produce a very low value
(large width/height encoded in a small number of bits because of static content)
and hence a low score. So, the old loss based thresholding is used.
For connection quality based on bitrate for down tracks, the measured rate should be used. That is to ensure that down track quality measurement does not get affected by publisher side changes negatively (or positively). Report the optimal bit rate to connection quality scorer every second so that scorer has a continuously updating picture of the stream and can compare the actual bit rate against expected optimal bitrate more reliably. Doing it at time like allocation, the bitrate may not be accurate (or may not even be available). So, a periodic update is necessary.
- track no layer expected case - always update transition - always call updateScore
davidzhao
approved these changes
Mar 5, 2023
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Follow up to connection quality changes. There was a missing bit in #1490, i. e. DownTrack running in deficient mode was not penalised based on not being to send desired layer(s).
To address that, two things
the measured rate should be used. That is to ensure that
down track quality measurement does not get affected by
publisher side changes negatively (or positively).
Report the optimal bit rate to connection quality scorer
every second so that scorer has a continuously updating
picture of the stream and can compare the actual bit rate
against expected optimal bitrate more reliably.
Doing it just at allocation time, the bitrate may not be
accurate (or may not even be available). So, a periodic update
is necessary.