install go2rtc on bob

installs_on_host/go2rtc/pkg/webrtc/server.go

@@ -0,0 +1,123 @@
+package webrtc
+
+import (
+	"github.com/AlexxIT/go2rtc/pkg/core"
+	"github.com/pion/sdp/v3"
+	"github.com/pion/webrtc/v4"
+)
+
+func (c *Conn) SetOffer(offer string) (err error) {
+	c.offer = offer
+
+	sd := &sdp.SessionDescription{}
+	if err = sd.Unmarshal([]byte(offer)); err != nil {
+		return
+	}
+
+	// create transceivers with opposite direction
+	for _, md := range sd.MediaDescriptions {
+		var mid string
+		var tr *webrtc.RTPTransceiver
+		for _, attr := range md.Attributes {
+			switch attr.Key {
+			case core.DirectionSendRecv:
+				tr, _ = c.pc.AddTransceiverFromTrack(NewTrack(md.MediaName.Media))
+			case core.DirectionSendonly:
+				tr, _ = c.pc.AddTransceiverFromKind(
+					webrtc.NewRTPCodecType(md.MediaName.Media),
+					webrtc.RTPTransceiverInit{Direction: webrtc.RTPTransceiverDirectionRecvonly},
+				)
+			case core.DirectionRecvonly:
+				tr, _ = c.pc.AddTransceiverFromTrack(
+					NewTrack(md.MediaName.Media),
+					webrtc.RTPTransceiverInit{Direction: webrtc.RTPTransceiverDirectionSendonly},
+				)
+			case "mid":
+				mid = attr.Value
+			}
+		}
+
+		if mid != "" && tr != nil {
+			_ = tr.SetMid(mid)
+		}
+	}
+
+	c.Medias = UnmarshalMedias(sd.MediaDescriptions)
+
+	return
+}
+
+func (c *Conn) GetAnswer() (answer string, err error) {
+	// we need to process remote offer after we create transeivers
+	desc := webrtc.SessionDescription{Type: webrtc.SDPTypeOffer, SDP: c.offer}
+	if err = c.pc.SetRemoteDescription(desc); err != nil {
+		return "", err
+	}
+
+	// disable transceivers if we don't have track, make direction=inactive
+transeivers:
+	for _, tr := range c.pc.GetTransceivers() {
+		for _, sender := range c.Senders {
+			if sender.Media.ID == tr.Mid() {
+				continue transeivers
+			}
+		}
+
+		switch tr.Direction() {
+		case webrtc.RTPTransceiverDirectionSendrecv:
+			_ = tr.Sender().Stop()             // don't know if necessary
+			_ = tr.SetSender(tr.Sender(), nil) // set direction to recvonly
+		case webrtc.RTPTransceiverDirectionSendonly:
+			_ = tr.Stop()
+		}
+	}
+
+	if desc, err = c.pc.CreateAnswer(nil); err != nil {
+		return
+	}
+	if err = c.pc.SetLocalDescription(desc); err != nil {
+		return
+	}
+
+	return c.pc.LocalDescription().SDP, nil
+}
+
+// GetCompleteAnswer - get SDP answer with candidates inside
+func (c *Conn) GetCompleteAnswer(candidates []string, filter func(*webrtc.ICECandidate) bool) (string, error) {
+	var done = make(chan struct{})
+
+	c.pc.OnICECandidate(func(candidate *webrtc.ICECandidate) {
+		if candidate != nil {
+			if filter == nil || filter(candidate) {
+				candidates = append(candidates, candidate.ToJSON().Candidate)
+			}
+		} else {
+			done <- struct{}{}
+		}
+	})
+
+	answer, err := c.GetAnswer()
+	if err != nil {
+		return "", err
+	}
+
+	<-done
+
+	sd := &sdp.SessionDescription{}
+	if err = sd.Unmarshal([]byte(answer)); err != nil {
+		return "", err
+	}
+
+	md := sd.MediaDescriptions[0]
+
+	for _, candidate := range candidates {
+		md.WithPropertyAttribute(candidate)
+	}
+
+	b, err := sd.Marshal()
+	if err != nil {
+		return "", err
+	}
+
+	return string(b), nil
+}