Merge pull request #1432 from seydx/rtsp-backchannel

Author: AlexxIT

internal/rtsp/rtsp.go

@@ -186,6 +186,22 @@ func tcpHandler(conn *rtsp.Conn) {
 				}
 			}
 
+			if query.Get("backchannel") == "1" {
+				conn.Medias = append(conn.Medias, &core.Media{
+					Kind:      core.KindAudio,
+					Direction: core.DirectionRecvonly,
+					Codecs: []*core.Codec{
+						{Name: core.CodecOpus, ClockRate: 48000, Channels: 2},
+						{Name: core.CodecPCM, ClockRate: 16000},
+						{Name: core.CodecPCMA, ClockRate: 16000},
+						{Name: core.CodecPCMU, ClockRate: 16000},
+						{Name: core.CodecPCM, ClockRate: 8000},
+						{Name: core.CodecPCMA, ClockRate: 8000},
+						{Name: core.CodecPCMU, ClockRate: 8000},
+					},
+				})
+			}
+
 			if s := query.Get("pkt_size"); s != "" {
 				conn.PacketSize = uint16(core.Atoi(s))
 			}

pkg/core/media.go

@@ -141,6 +141,10 @@ func MarshalSDP(name string, medias []*Media) ([]byte, error) {
 		}
 		md.WithCodec(codec.PayloadType, name, codec.ClockRate, codec.Channels, codec.FmtpLine)
 
+		if media.Direction != "" {
+			md.WithPropertyAttribute(media.Direction)
+		}
+
 		if media.ID != "" {
 			md.WithValueAttribute("control", media.ID)
 		}

pkg/rtsp/producer.go

@@ -19,19 +19,30 @@ func (c *Conn) GetTrack(media *core.Media, codec *core.Codec) (*core.Receiver, e
 	c.stateMu.Lock()
 	defer c.stateMu.Unlock()
 
-	if c.state == StatePlay {
-		if err := c.Reconnect(); err != nil {
+	var channel byte
+
+	switch c.mode {
+	case core.ModeActiveProducer:
+		if c.state == StatePlay {
+			if err := c.Reconnect(); err != nil {
+				return nil, err
+			}
+		}
+
+		var err error
+		channel, err = c.SetupMedia(media)
+		if err != nil {
 			return nil, err
 		}
-	}
 
-	channel, err := c.SetupMedia(media)
-	if err != nil {
-		return nil, err
+		c.state = StateSetup
+	case core.ModePassiveConsumer:
+		// Backchannel
+		channel = byte(len(c.Senders)) * 2
+	default:
+		return nil, errors.New("rtsp: wrong mode for GetTrack")
 	}
 
-	c.state = StateSetup
-
 	track := core.NewReceiver(media, codec)
 	track.ID = channel
 	c.Receivers = append(c.Receivers, track)

pkg/rtsp/server.go

@@ -136,6 +136,16 @@ func (c *Conn) Accept() error {
 				medias = append(medias, media)
 			}
 
+			for i, track := range c.Receivers {
+				media := &core.Media{
+					Kind:      core.GetKind(track.Codec.Name),
+					Direction: core.DirectionSendonly,
+					Codecs:    []*core.Codec{track.Codec},
+					ID:        "trackID=" + strconv.Itoa(i+len(c.Senders)),
+				}
+				medias = append(medias, media)
+			}
+
 			res.Body, err = core.MarshalSDP(c.SessionName, medias)
 			if err != nil {
 				return err
@@ -160,9 +170,12 @@ func (c *Conn) Accept() error {
 				c.state = StateSetup
 
 				if c.mode == core.ModePassiveConsumer {
-					if i := reqTrackID(req); i >= 0 && i < len(c.Senders) {
-						// mark sender as SETUP
-						c.Senders[i].Media.ID = MethodSetup
+					if i := reqTrackID(req); i >= 0 && i < len(c.Senders)+len(c.Receivers) {
+						if i < len(c.Senders) {
+							c.Senders[i].Media.ID = MethodSetup
+						} else {
+							c.Receivers[i-len(c.Senders)].Media.ID = MethodSetup
+						}
 						tr = fmt.Sprintf("RTP/AVP/TCP;unicast;interleaved=%d-%d", i*2, i*2+1)
 						res.Header.Set("Transport", tr)
 					} else {