Add support for multi codec negotiation

Author: itzmanish

mediaengine.go

@@ -33,6 +33,7 @@ type mediaEngineHeaderExtension struct {
 type MediaEngine struct {
 	// If we have attempted to negotiate a codec type yet.
 	negotiatedVideo, negotiatedAudio bool
+	negotiateMultiCodecs             bool
 
 	videoCodecs, audioCodecs                     []RTPCodecParameters
 	negotiatedVideoCodecs, negotiatedAudioCodecs []RTPCodecParameters
@@ -43,6 +44,22 @@ type MediaEngine struct {
 	mu sync.RWMutex
 }
 
+// SetMultiCodecNegotiation enables or disables the negotiation of multiple codecs.
+func (m *MediaEngine) SetMultiCodecNegotiation(negotiateMultiCodecs bool) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	m.negotiateMultiCodecs = negotiateMultiCodecs
+}
+
+// MultiCodecNegotiation returns the current state of the negotiation of multiple codecs.
+func (m *MediaEngine) MultiCodecNegotiation() bool {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	return m.negotiateMultiCodecs
+}
+
 // RegisterDefaultCodecs registers the default codecs supported by Pion WebRTC.
 // RegisterDefaultCodecs is not safe for concurrent use.
 func (m *MediaEngine) RegisterDefaultCodecs() error {
@@ -579,9 +596,9 @@ func (m *MediaEngine) updateFromRemoteDescription(desc sdp.SessionDescription) e
 		}
 
 		switch {
-		case !m.negotiatedAudio && typ == RTPCodecTypeAudio:
+		case (!m.negotiatedAudio || m.negotiateMultiCodecs) && typ == RTPCodecTypeAudio:
 			m.negotiatedAudio = true
-		case !m.negotiatedVideo && typ == RTPCodecTypeVideo:
+		case (!m.negotiatedVideo || m.negotiateMultiCodecs) && typ == RTPCodecTypeVideo:
 			m.negotiatedVideo = true
 		default:
 			// update header extesions from remote sdp if codec is negotiated, Firefox

mediaengine_test.go

@@ -896,3 +896,68 @@ a=rtcp-fb:96 nack
 		runTest(t, true)
 	})
 }
+
+func TestMultiCodecNegotiation(t *testing.T) {
+	const offerSdp = `v=0
+o=- 781500112831855234 6 IN IP4 127.0.0.1
+s=-
+t=0 0
+a=group:BUNDLE 0 1 2 3
+a=extmap-allow-mixed
+a=msid-semantic: WMS be0216be-f3d8-40ca-a624-379edf70f1c9
+m=application 53555 UDP/DTLS/SCTP webrtc-datachannel
+a=mid:0
+a=sctp-port:5000
+a=max-message-size:262144
+m=video 9 UDP/TLS/RTP/SAVPF 98
+a=mid:1
+a=sendonly
+a=msid:be0216be-f3d8-40ca-a624-379edf70f1c9 3d032b3b-ffe5-48ec-b783-21375668d1c3
+a=rtcp-mux
+a=rtcp-rsize
+a=rtpmap:98 VP9/90000
+a=rtcp-fb:98 goog-remb
+a=rtcp-fb:98 transport-cc
+a=rtcp-fb:98 ccm fir
+a=rtcp-fb:98 nack
+a=rtcp-fb:98 nack pli
+a=fmtp:98 profile-id=0
+a=rid:q send
+a=rid:h send
+a=simulcast:send q;h
+m=video 9 UDP/TLS/RTP/SAVPF 96
+a=mid:2
+a=sendonly
+a=msid:6ff05509-be96-4ef1-a74f-425e14720983 16d5d7fe-d076-4718-9ca9-ec62b4543727
+a=rtcp-mux
+a=rtcp-rsize
+a=rtpmap:96 VP8/90000
+a=rtcp-fb:96 goog-remb
+a=rtcp-fb:96 transport-cc
+a=rtcp-fb:96 ccm fir
+a=rtcp-fb:96 nack
+a=rtcp-fb:96 nack pli
+a=ssrc:4281768245 cname:JDM9GNMEg+9To6K7
+a=ssrc:4281768245 msid:6ff05509-be96-4ef1-a74f-425e14720983 16d5d7fe-d076-4718-9ca9-ec62b4543727
+`
+	mustParse := func(raw string) sdp.SessionDescription {
+		s := sdp.SessionDescription{}
+		assert.NoError(t, s.Unmarshal([]byte(raw)))
+
+		return s
+	}
+	t.Run("Multi codec negotiation disabled", func(t *testing.T) {
+		mediaEngine := MediaEngine{}
+		assert.NoError(t, mediaEngine.RegisterDefaultCodecs())
+		assert.NoError(t, mediaEngine.updateFromRemoteDescription(mustParse(offerSdp)))
+		assert.Len(t, mediaEngine.negotiatedVideoCodecs, 1)
+	})
+	t.Run("Multi codec negotiation enabled", func(t *testing.T) {
+		mediaEngine := MediaEngine{}
+		mediaEngine.SetMultiCodecNegotiation(true)
+		assert.True(t, mediaEngine.MultiCodecNegotiation())
+		assert.NoError(t, mediaEngine.RegisterDefaultCodecs())
+		assert.NoError(t, mediaEngine.updateFromRemoteDescription(mustParse(offerSdp)))
+		assert.Len(t, mediaEngine.negotiatedVideoCodecs, 2)
+	})
+}