Connection quality misc changes (#1496)

* 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

pkg/sfu/buffer/rtpstats.go

@@ -864,6 +864,10 @@ func (r *RTPStats) DeltaInfo(snapshotId uint32) *RTPDeltaInfo {
 		return nil
 	}
 	if packetsExpected == 0 {
+		r.logger.Debugw(
+			"no expected packets",
+			"info", fmt.Sprintf("start: %d @ %+v, end: %d @ %+v", then.extStartSN, then.startTime, now.extStartSN, now.startTime),
+		)
 		return nil
 	}
 
@@ -873,10 +877,15 @@ func (r *RTPStats) DeltaInfo(snapshotId uint32) *RTPDeltaInfo {
 		// by taking number of packets from interval report, packets not sent (because of missing packets in feed) will be accounted for
 		packetsExpected = intervalStats.packets + intervalStats.packetsPadding
 		if packetsExpected == 0 {
+			r.logger.Debugw(
+				"no expected packets in interval",
+				"info", fmt.Sprintf("start: %d @ %+v, end: %d @ %+v", then.extStartSN, then.startTime, now.extStartSN, now.startTime),
+			)
 			return nil
 		}
 
-		packetsLost = now.packetsLostOverridden - then.packetsLostOverridden
+		// discount loss in the interval as those are packets not sent at all
+		packetsLost = now.packetsLostOverridden - then.packetsLostOverridden - intervalStats.packetsLost
 		if int32(packetsLost) < 0 {
 			packetsLost = 0
 		}
@@ -884,7 +893,14 @@ func (r *RTPStats) DeltaInfo(snapshotId uint32) *RTPDeltaInfo {
 		if packetsLost > packetsExpected {
 			r.logger.Warnw(
 				"unexpected number of packets lost",
-				fmt.Errorf("start: %d, end: %d, expected: %d, lost: %d", then.extStartSN, now.extStartSN, packetsExpected, packetsLost),
+				fmt.Errorf(
+					"start: %d, end: %d, expected: %d, lost: report: %d, interval: %d",
+					then.extStartSN,
+					now.extStartSN,
+					packetsExpected,
+					now.packetsLostOverridden-then.packetsLostOverridden,
+					intervalStats.packetsLost,
+				),
 			)
 			packetsLost = packetsExpected
 		}
@@ -1123,12 +1139,12 @@ func (r *RTPStats) getSnInfoOutOfOrderPtr(sn uint16) int {
 	offset := sn - r.highestSN
 	if offset > 0 && offset < (1<<15) {
 		return -1 // in-order, not expected, maybe too new
-	} else {
-		offset = r.highestSN - sn
-		if int(offset) >= SnInfoSize {
-			// too old, ignore
-			return -1
-		}
+	}
+
+	offset = r.highestSN - sn
+	if int(offset) >= SnInfoSize {
+		// too old, ignore
+		return -1
 	}
 
 	return (r.snInfoWritePtr - int(offset) - 1) & SnInfoMask
@@ -1180,6 +1196,7 @@ func (r *RTPStats) getIntervalStats(startInclusive uint16, endExclusive uint16)
 	processSN := func(sn uint16) {
 		readPtr := r.getSnInfoOutOfOrderPtr(sn)
 		if readPtr < 0 {
+			packetsNotFound++
 			return
 		}
 

pkg/sfu/connectionquality/connectionstats.go

@@ -77,25 +77,29 @@ func (cs *ConnectionStats) GetScoreAndQuality() (float32, livekit.ConnectionQual
 }
 
 func (cs *ConnectionStats) updateScore(streams map[uint32]*buffer.StreamStatsWithLayers, at time.Time) float32 {
-	var stat windowStat
-	for _, s := range streams {
-		if stat.startedAt.IsZero() || stat.startedAt.After(s.RTPStats.StartTime) {
-			stat.startedAt = s.RTPStats.StartTime
+	if len(streams) == 0 {
+		cs.scorer.Update(nil, at)
+	} else {
+		var stat windowStat
+		for _, s := range streams {
+			if stat.startedAt.IsZero() || stat.startedAt.After(s.RTPStats.StartTime) {
+				stat.startedAt = s.RTPStats.StartTime
+			}
+			if stat.duration < s.RTPStats.Duration {
+				stat.duration = s.RTPStats.Duration
+			}
+			stat.packetsExpected += s.RTPStats.Packets + s.RTPStats.PacketsPadding
+			stat.packetsLost += s.RTPStats.PacketsLost
+			if stat.rttMax < s.RTPStats.RttMax {
+				stat.rttMax = s.RTPStats.RttMax
+			}
+			if stat.jitterMax < s.RTPStats.JitterMax {
+				stat.jitterMax = s.RTPStats.JitterMax
+			}
+			stat.bytes += s.RTPStats.Bytes - s.RTPStats.HeaderBytes // only use media payload size
 		}
-		if stat.duration < s.RTPStats.Duration {
-			stat.duration = s.RTPStats.Duration
-		}
-		stat.packetsExpected += s.RTPStats.Packets + s.RTPStats.PacketsPadding
-		stat.packetsLost += s.RTPStats.PacketsLost
-		if stat.rttMax < s.RTPStats.RttMax {
-			stat.rttMax = s.RTPStats.RttMax
-		}
-		if stat.jitterMax < s.RTPStats.JitterMax {
-			stat.jitterMax = s.RTPStats.JitterMax
-		}
-		stat.bytes += s.RTPStats.Bytes - s.RTPStats.HeaderBytes // only use media payload size
+		cs.scorer.Update(&stat, at)
 	}
-	cs.scorer.Update(&stat, at)
 
 	mos, _ := cs.scorer.GetMOSAndQuality()
 	return mos

pkg/sfu/connectionquality/scorer.go

@@ -50,7 +50,12 @@ func (w *windowStat) calculatePacketScore(plw float64) float64 {
 	}
 	lossEffect *= plw
 
-	return maxScore - delayEffect - lossEffect
+	score := maxScore - delayEffect - lossEffect
+	if score < 0.0 {
+		score = 0.0
+	}
+
+	return score
 }
 
 func (w *windowStat) calculateByteScore(expectedBitrate int64) float64 {
@@ -286,7 +291,7 @@ func (q *qualityScorer) Update(stat *windowStat, at time.Time) {
 		q.score = score
 		q.params.Logger.Infow(
 			"quality drop",
-			"reaason", reason,
+			"reason", reason,
 			"score", q.score,
 			"quality", scoreToConnectionQuality(q.score),
 			"window", ws,