client, server: print number of lost packets even when using TCP (#269)

pkg/rtplossdetector/lossdetector.go

@@ -0,0 +1,36 @@
+// Package rtplossdetector implements an algorithm that detects lost packets.
+package rtplossdetector
+
+import (
+	"github.com/pion/rtp"
+)
+
+// LossDetector detects lost packets.
+type LossDetector struct {
+	initialized    bool
+	expectedSeqNum uint16
+}
+
+// New allocates a LossDetector.
+func New() *LossDetector {
+	return &LossDetector{}
+}
+
+// Process processes a RTP packet.
+// It returns the number of lost packets.
+func (r *LossDetector) Process(pkt *rtp.Packet) int {
+	if !r.initialized {
+		r.initialized = true
+		r.expectedSeqNum = pkt.SequenceNumber + 1
+		return 0
+	}
+
+	if pkt.SequenceNumber != r.expectedSeqNum {
+		diff := pkt.SequenceNumber - r.expectedSeqNum
+		r.expectedSeqNum = pkt.SequenceNumber + 1
+		return int(diff)
+	}
+
+	r.expectedSeqNum = pkt.SequenceNumber + 1
+	return 0
+}