skip lost sequence number ranges in getIntervalStats (#4166)

pkg/sfu/rtpstats/rtpstats_sender.go

@@ -1268,13 +1268,18 @@ func (r *RTPStatsSender) getIntervalStats(
 	extEndExclusive uint64,
 	ehsn uint64,
 ) (intervalStats intervalStats) {
-	processESN := func(esn uint64, ehsn uint64) {
-		slot := r.getSnInfoOutOfOrderSlot(esn, ehsn)
-		if slot < 0 {
-			intervalStats.packetsNotFoundMetadata++
-			return
-		}
+	upperBound := ehsn + 1
+	lowerBound := uint64(0)
+	if n := uint64(len(r.snInfos)); n != 0 && ehsn >= n-1 {
+		lowerBound = ehsn - n + 1
+	}
+	extStartInclusiveClamped := max(min(extStartInclusive, upperBound), lowerBound)
+	extEndExclusiveClamped := max(min(extEndExclusive, upperBound), extStartInclusive)
 
+	intervalStats.packetsNotFoundMetadata += (extEndExclusive - extStartInclusive) - (extEndExclusiveClamped - extStartInclusiveClamped)
+
+	for esn := extStartInclusiveClamped; esn != extEndExclusiveClamped; esn++ {
+		slot := r.getSnInfoOutOfOrderSlot(esn, ehsn)
 		snInfo := &r.snInfos[slot]
 		switch {
 		case snInfo.pktSize == 0:
@@ -1298,10 +1303,6 @@ func (r *RTPStatsSender) getIntervalStats(
 			intervalStats.frames++
 		}
 	}
-
-	for esn := extStartInclusive; esn != extEndExclusive; esn++ {
-		processESN(esn, ehsn)
-	}
 	return
 }