* Ensure sequence number continuity
When using Go SDK (livekit-cli or egress) as a client,
SFU sends blank frames when audio track is muted to ensure that
Pion OnTrack fires on GoSDK side. That resulted in a huge sequence
number/time stamp jump when the real stream started.
Ensure continuity by creating random sequence number/time stamp when
starting with a blank frames. And when sequence number/time stamp is
initialized using SetLastSnTs, continue sequence if it was already
initialized.
* remove debug
A few more candidates to think about demoting
- Publisher mute changes
- Forwarder -> layer lock/upgrade/downgrade/overshoot adjusting
- StreamAllocator
* Discount upstream + processing jitter from down stream jitter.
Jitter in RTCP Receiver Report from down stream tracks includes
jitter from up stream tracks and any processing in forwarding path.
As packets are forwarded without any buffering (i. e. no de-jittering)
in the SFU, any up stream jitter will carry forward.
While taking delta stats (which is used for connection quality and
reporting to analytics), discount the up stream + processing jitter so
that connection quality score of down stream track is not penalized
due to up stream + processing jitter.
NOTE: Not discounting it in RTP stats ToString/ToProto methods as
that information is useful to have for analysis/debugging.
* fix typo
A few things
1. Have to use expected layer in upstream distance to desired. Using
min(published, expected) means if expected is higher than published, it was not caught as a missed layer.
2. Forgot to remove layer transition update in one place. It was still constrained to screen share.
This caused quality to not pick up after constraint is released.
3. Switching to max layer cannot be marked on max published. Same as point #1 above. Otherwise,
dynacast would kick in and turn off highest layer.
There are cases where the layer bit rate configuration is such that
the expected bitrate difference is very high. For example,
setting up layer 2 (f) layer for 1.7 Mbps and layer 1 (h) for 180 kbps.
With bitrate based quality, a layer drop results in going to `POOR`
quality rating. With layer based, it will drop one level only.
Also, cleaning up the distance to desired calculation a bit.
With push model (i. e. connection quality evaluation triggered
by reception of RTCP receiver report), it is possible that a report
is received quickly after a track is started (especially with video).
Those should not trigger a quality evaluation.
Set `lastStatsAt` in `Start` routine and ensure that start has been
called and enough time has passed since last stats time to avoid
small windows.
* Expected vs actual Layer based connection quality.
With VBR streams (like screen share), bit rate is not a good indicator
of whether desired layer (spatial/temporal) is achieved due to high
variance.
Using expected vs actual layer (i. e. distance to desired) can capture
any short fall and include it in quality scoring.
This PR uses distance to desired, i. e. how many steps it would take to
go from actual spatial/temporal -> desired spatial/temporal and that
distance is propotionally used (currently it is just linear) to decrease
score.
* wire up layer transitions for screen share tracks
* Use EWMA (Exponentially Weighted Moving Average) for score updates.
Makes code simpler, but makes it harder to test as the inflection points
are not exact.
Score falls a bit slower to be conservative on dropping quality too
quickly. Still fall factor is higher (i. e. newer scores get more
weight) than rise factor (i. e. newer scores get lower weight).
Slower rise factor to introduce hysteresis on things climibing back too
quickly.
In the extreme case, asympttotic conditions could cause unexpected
results. For example, having 4% loss of video continously will never
drop quality to `POOR`. It will get close to 60, but it will always
stay above 60 forever and hence quality will never drop to POOR.
Maybe, need some sort of variable thresholding to deal with that. But,
that is an extreme case and may not happen in real life.
* remove unused stuff
* Push/pull for connection stats/quality scoring.
Was not happy with pure pull method missing a window because
of RTCP RR timing is slightly off for audio and using a much
larger window of data in the next update.
That also resulted in RTP stats getting some bits of code.
As that is per-packet processing, was not a good idea.
Switching to push-pull method.
For up track, it is pull, i. e. connection stats worker will pull stats.
For down track, there is a new notification about receiver report
reception. Using this to check for time to run stats. And adding a bit
of tolerance for processing window (currently set so that as long as it
is > 95% of usual processing interval). This allows two things
- for video, RTCP RR are more frequent, but we will still not process
till enough time has passed
- for audio, RTCP RR could be once in 5 seconds or so. Can process when
it is available rather than miss a window and use a much larger window
later.
* uber atomic
* Connectino quality misc changes
1. Call scorer.Update() with nil stat when no data available so that
scorer can synthesise window with proper window time.
2. Substract out loss in interval to account for packets not sent at
all.
3. Fix `packetsNotFound` variable in `getIntervalStats`. I remember this
working at some point. Not sure if I fat fingered in another PR and
deleted the increment line.
4. Logging a bit more when no packets expected. Those can get noisy
especially when track is muted. But, seeing some unexplained
instances of no packets leading to quality drop. So, temporary logging
to get a bit more information.
* correct spelling
* Limit packet score minimum to 0.0
* Make connection quality not too optimistic.
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.
* clean up
* update rtcscore pointer
* fix tests
* log lines reformat
* WIP commit
* WIP commit
* update mute of receiver
* WIP commit
* WIP commit
* start adding tests
* take min score if quality matches
* start adding bytes based scoring
* clean up
* more clean up
* Use Fuse
* log quality drop
* Periodically report bitrate to down track.
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.
* add transition at allocation times
* clean up debug log
* - Use number of windows for wait to make things simpler
- track no layer expected case
- always update transition
- always call updateScore
* Make connection quality not too optimistic.
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.
* clean up
* update rtcscore pointer
* fix tests
* log lines reformat
* WIP commit
* WIP commit
* update mute of receiver
* WIP commit
* WIP commit
* start adding tests
* take min score if quality matches
* start adding bytes based scoring
* clean up
* more clean up
* Use Fuse
* log quality drop
* clean up debug log
* - Use number of windows for wait to make things simpler
- track no layer expected case
- always update transition
- always call updateScore
David Zhao