rtcpsender: extract clock rate from sdp instead of estimating it

connclient.go

@@ -503,11 +503,6 @@ func (c *ConnClient) Setup(u *base.URL, mode headers.TransportMode, proto base.S
 		}
 	}
 
-	c.streamUrl = u
-	c.streamProtocol = &proto
-
-	c.tracks = append(c.tracks, track)
-
 	if mode == headers.TransportModePlay {
 		c.rtcpReceivers[track.Id] = rtcpreceiver.New(nil)
 
@@ -516,8 +511,16 @@ func (c *ConnClient) Setup(u *base.URL, mode headers.TransportMode, proto base.S
 			c.udpLastFrameTimes[track.Id] = &v
 		}
 	} else {
-		c.rtcpSenders[track.Id] = rtcpsender.New()
+		clockRate, err := track.ClockRate()
+		if err != nil {
+			return nil, fmt.Errorf("unable to get track clock rate: %s", err)
 		}
+		c.rtcpSenders[track.Id] = rtcpsender.New(clockRate)
+	}
+
+	c.streamUrl = u
+	c.streamProtocol = &proto
+	c.tracks = append(c.tracks, track)
 
 	if proto == StreamProtocolUDP {
 		rtpListener.remoteIp = c.nconn.RemoteAddr().(*net.TCPAddr).IP

pkg/rtcpreceiver/rtcpreceiver.go

@@ -12,10 +12,10 @@ import (
 
 // RtcpReceiver allows to generate RTCP receiver reports.
 type RtcpReceiver struct {
+	receiverSSRC         uint32
 	mutex                sync.Mutex
 	firstRtpReceived     bool
 	senderSSRC           uint32
-	receiverSSRC         uint32
 	sequenceNumberCycles uint16
 	lastSequenceNumber   uint16
 	lastSenderReportTime uint32

pkg/rtcpsender/rtcpsender.go

@@ -13,20 +13,21 @@ import (
 
 // RtcpSender allows to generate RTCP sender reports.
 type RtcpSender struct {
+	clockRate        float64
 	mutex            sync.Mutex
 	firstRtpReceived bool
-	secondRtpReceived bool
 	senderSSRC       uint32
-	packetCount       uint32
-	octetCount        uint32
 	rtpTimeOffset    uint32
 	rtpTimeTime      time.Time
-	clock             float64
+	packetCount      uint32
+	octetCount       uint32
 }
 
 // New allocates a RtcpSender.
-func New() *RtcpSender {
+func New(clockRate int) *RtcpSender {
-	return &RtcpSender{}
+	return &RtcpSender{
+		clockRate: float64(clockRate),
+	}
 }
 
 // OnFrame processes a RTP or RTCP frame and extract the needed data.
@@ -45,13 +46,6 @@ func (rs *RtcpSender) OnFrame(ts time.Time, streamType base.StreamType, buf []by
 				// save RTP time offset and correspondent time
 				rs.rtpTimeOffset = pkt.Timestamp
 				rs.rtpTimeTime = ts
-
-			} else if !rs.secondRtpReceived && pkt.Timestamp != rs.rtpTimeOffset {
-				rs.secondRtpReceived = true
-
-				// estimate clock
-				rs.clock = float64(pkt.Timestamp-rs.rtpTimeOffset) /
-					ts.Sub(rs.rtpTimeTime).Seconds()
 			}
 
 			rs.packetCount++
@@ -65,7 +59,7 @@ func (rs *RtcpSender) Report(ts time.Time) []byte {
 	rs.mutex.Lock()
 	defer rs.mutex.Unlock()
 
-	if !rs.firstRtpReceived || !rs.secondRtpReceived {
+	if !rs.firstRtpReceived {
 		return nil
 	}
 
@@ -73,14 +67,14 @@ func (rs *RtcpSender) Report(ts time.Time) []byte {
 		SSRC: rs.senderSSRC,
 		NTPTime: func() uint64 {
 			// seconds since 1st January 1900
-			n := (float64(ts.UnixNano()) / 1000000000) + 2208988800
+			s := (float64(ts.UnixNano()) / 1000000000) + 2208988800
 
 			// higher 32 bits are the integer part, lower 32 bits are the fractional part
-			integerPart := uint32(n)
+			integerPart := uint32(s)
-			fractionalPart := uint32((n - float64(integerPart)) * 0xFFFFFFFF)
+			fractionalPart := uint32((s - float64(integerPart)) * 0xFFFFFFFF)
 			return uint64(integerPart)<<32 | uint64(fractionalPart)
 		}(),
-		RTPTime:     rs.rtpTimeOffset + uint32((ts.Sub(rs.rtpTimeTime)).Seconds()*rs.clock),
+		RTPTime:     rs.rtpTimeOffset + uint32((ts.Sub(rs.rtpTimeTime)).Seconds()*float64(rs.clockRate)),
 		PacketCount: rs.packetCount,
 		OctetCount:  rs.octetCount,
 	}

pkg/rtpaac/encoder.go

@@ -19,7 +19,7 @@ const (
 // Encoder is a RPT/AAC encoder.
 type Encoder struct {
 	payloadType    uint8
-	samplingRate   float64
+	sampleRate     float64
 	sequenceNumber uint16
 	ssrc           uint32
 	initialTs      uint32
@@ -35,7 +35,7 @@ func NewEncoder(relativeType uint8, config []byte) (*Encoder, error) {
 
 	return &Encoder{
 		payloadType:    96 + relativeType,
-		samplingRate:   float64(codec.Config.SampleRate),
+		sampleRate:     float64(codec.Config.SampleRate),
 		sequenceNumber: uint16(rand.Uint32()),
 		ssrc:           rand.Uint32(),
 		initialTs:      rand.Uint32(),
@@ -52,7 +52,7 @@ func (e *Encoder) Write(data []byte, timestamp time.Duration) ([][]byte, error)
 		return nil, fmt.Errorf("data is too big")
 	}
 
-	rtpTs := e.initialTs + uint32((timestamp-e.started).Seconds()*e.samplingRate)
+	rtpTs := e.initialTs + uint32((timestamp-e.started).Seconds()*e.sampleRate)
 
 	// 13 bits payload size
 	// 3 bits AU-Index(-delta)

track.go

@@ -107,6 +107,32 @@ func NewTrackAac(id int, config []byte) (*Track, error) {
 	}, nil
 }
 
+// ClockRate returns the clock rate of the track.
+func (t *Track) ClockRate() (int, error) {
+	// https://tools.ietf.org/html/rfc4566
+	// a=rtpmap:<payload type> <encoding name>/<clock rate> [/<encoding parameters>]
+	for _, a := range t.Media.Attributes {
+		if a.Key == "rtpmap" {
+			tmp := strings.Split(a.Value, " ")
+			if len(tmp) != 2 {
+				return 0, fmt.Errorf("invalid format (%s)", a.Value)
+			}
+
+			tmp = strings.Split(tmp[1], "/")
+			if len(tmp) != 2 && len(tmp) != 3 {
+				return 0, fmt.Errorf("invalid format (%s)", a.Value)
+			}
+
+			v, err := strconv.ParseInt(tmp[1], 10, 64)
+			if err != nil {
+				return 0, err
+			}
+			return int(v), nil
+		}
+	}
+	return 0, fmt.Errorf("attribute 'rtpmap' not found")
+}
+
 // Tracks is a list of tracks.
 type Tracks []*Track