Restrict negotiation of downstream codecs, allow multiple profiles.

We now restrict the allowable codecs in the downstream direction,
which leads to a clean failure instead of a silent track.  We also
allow multiple profiles for a single codec.

group/group.go

@@ -142,71 +142,49 @@ func (g *Group) API() (*webrtc.API, error) {
 	return APIFromNames(codecs)
 }
 
-func codecFromName(name string) (webrtc.RTPCodecCapability, error) {
+func fmtpValue(fmtp, key string) string {
-	switch name {
+	fields := strings.Split(fmtp, ";")
-	case "vp8":
+	for _, f := range fields {
-		return webrtc.RTPCodecCapability{
+		kv := strings.SplitN(f, "=", 2)
-			"video/VP8", 90000, 0,
+		if len(kv) != 2 {
-			"",
+			continue
-			nil,
-		}, nil
-	case "vp9":
-		return webrtc.RTPCodecCapability{
-			"video/VP9", 90000, 0,
-			"profile-id=0",
-			nil,
-		}, nil
-	case "av1":
-		return webrtc.RTPCodecCapability{
-			"video/AV1X", 90000, 0,
-			"",
-			nil,
-		}, nil
-	case "h264":
-		return webrtc.RTPCodecCapability{
-			"video/H264", 90000, 0,
-			"level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f",
-			nil,
-		}, nil
-	case "opus":
-		return webrtc.RTPCodecCapability{
-			"audio/opus", 48000, 2,
-			"minptime=10;useinbandfec=1;stereo=1;sprop-stereo=1",
-			nil,
-		}, nil
-	case "g722":
-		return webrtc.RTPCodecCapability{
-			"audio/G722", 8000, 1,
-			"",
-			nil,
-		}, nil
-	case "pcmu":
-		return webrtc.RTPCodecCapability{
-			"audio/PCMU", 8000, 1,
-			"",
-			nil,
-		}, nil
-	case "pcma":
-		return webrtc.RTPCodecCapability{
-			"audio/PCMA", 8000, 1,
-			"",
-			nil,
-		}, nil
-	default:
-		return webrtc.RTPCodecCapability{}, errors.New("unknown codec")
 		}
+		if kv[0] == key {
+			return kv[1]
+		}
+	}
+	return ""
 }
 
-func payloadType(codec webrtc.RTPCodecCapability) (webrtc.PayloadType, error) {
+func CodecPayloadType(codec webrtc.RTPCodecCapability) (webrtc.PayloadType, error) {
 	switch strings.ToLower(codec.MimeType) {
 	case "video/vp8":
 		return 96, nil
 	case "video/vp9":
+		profile := fmtpValue(codec.SDPFmtpLine, "profile-id")
+		switch(profile) {
+		case "0":
 			return 98, nil
+		case "2":
+			return 100, nil
+		default:
+			return 0, errors.New("unknown VP9 profile")
+		}
 	case "video/av1x":
-		return 104, nil
+		return 35, nil
 	case "video/h264":
+		profile := fmtpValue(codec.SDPFmtpLine, "profile-level-id")
+		if len(profile) < 4 {
+			return 0, errors.New("malforned H.264 profile")
+		}
+		switch(strings.ToLower(profile[:4])) {
+		case "4200":
 			return 102, nil
+		case "42e0":
+			return 108, nil
+		default:
+			return 0, errors.New("unknown H.264 profile")
+		}
 	case "audio/opus":
 		return 111, nil
 	case "audio/g722":
@@ -220,7 +198,112 @@ func payloadType(codec webrtc.RTPCodecCapability) (webrtc.PayloadType, error) {
 	}
 }
 
-func APIFromCodecs(codecs []webrtc.RTPCodecCapability) (*webrtc.API, error) {
+func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
+	fb := []webrtc.RTCPFeedback{
+		{"goog-remb", ""},
+		{"nack", ""},
+		{"nack", "pli"},
+		{"ccm", "fir"},
+	}
+
+	var codecs []webrtc.RTPCodecCapability
+
+	switch name {
+	case "vp8":
+		codecs = []webrtc.RTPCodecCapability{
+			{
+				"video/VP8", 90000, 0,
+				"",
+				fb,
+			},
+		}
+	case "vp9":
+		codecs = []webrtc.RTPCodecCapability{
+			{
+				"video/VP9", 90000, 0,
+				"profile-id=0",
+				fb,
+			},
+			{
+				"video/VP9", 90000, 0,
+				"profile-id=2",
+				fb,
+			},
+		}
+	case "av1":
+		codecs = []webrtc.RTPCodecCapability{
+			{
+				"video/AV1X", 90000, 0,
+				"",
+				fb,
+			},
+		}
+	case "h264":
+		codecs = []webrtc.RTPCodecCapability{
+			{
+				"video/H264", 90000, 0,
+				"level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f",
+				fb,
+			},
+			{
+				"video/H264", 90000, 0,
+				"level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f",
+				fb,
+			},
+		}
+	case "opus":
+		codecs = []webrtc.RTPCodecCapability{
+			{
+				"audio/opus", 48000, 2,
+				"minptime=10;useinbandfec=1;stereo=1;sprop-stereo=1",
+				nil,
+			},
+		}
+	case "g722":
+		codecs = []webrtc.RTPCodecCapability{
+			{
+				"audio/G722", 8000, 1,
+				"",
+				nil,
+			},
+		}
+	case "pcmu":
+		codecs = []webrtc.RTPCodecCapability{
+			{
+				"audio/PCMU", 8000, 1,
+				"",
+				nil,
+			},
+		}
+	case "pcma":
+		codecs = []webrtc.RTPCodecCapability{
+			{
+				"audio/PCMU", 8000, 1,
+				"",
+				nil,
+			},
+		}
+	default:
+		return nil, errors.New("unknown codec")
+	}
+
+	parms := make([]webrtc.RTPCodecParameters, 0, len(codecs))
+	for _, c := range codecs {
+		ptype, err := CodecPayloadType(c)
+		if err != nil {
+			log.Printf("Couldn't determine ptype for codec %v: %v",
+				c.MimeType, err)
+			continue
+		}
+		parms = append(parms, webrtc.RTPCodecParameters{
+			RTPCodecCapability: c,
+			PayloadType:        ptype,
+		})
+	}
+	return parms, nil
+}
+
+func APIFromCodecs(codecs []webrtc.RTPCodecParameters) (*webrtc.API, error) {
 	s := webrtc.SettingEngine{}
 	s.SetSRTPReplayProtectionWindow(512)
 	if !UseMDNS {
@@ -229,41 +312,11 @@ func APIFromCodecs(codecs []webrtc.RTPCodecCapability) (*webrtc.API, error) {
 	m := webrtc.MediaEngine{}
 
 	for _, codec := range codecs {
-		var tpe webrtc.RTPCodecType
+		tpe := webrtc.RTPCodecTypeVideo
-		var fb []webrtc.RTCPFeedback
+		if strings.HasPrefix(strings.ToLower(codec.MimeType), "audio/") {
-		if strings.HasPrefix(strings.ToLower(codec.MimeType), "video/") {
-			tpe = webrtc.RTPCodecTypeVideo
-			fb = []webrtc.RTCPFeedback{
-				{"goog-remb", ""},
-				{"nack", ""},
-				{"nack", "pli"},
-				{"ccm", "fir"},
-			}
-		} else if strings.HasPrefix(strings.ToLower(codec.MimeType), "audio/") {
 			tpe = webrtc.RTPCodecTypeAudio
-			fb = []webrtc.RTCPFeedback{}
-		} else {
-			continue
 		}
-
+		err := m.RegisterCodec(codec, tpe)
-		ptpe, err := payloadType(codec)
-		if err != nil {
-			log.Printf("%v", err)
-			continue
-		}
-		err = m.RegisterCodec(
-			webrtc.RTPCodecParameters{
-				RTPCodecCapability: webrtc.RTPCodecCapability{
-					MimeType:     codec.MimeType,
-					ClockRate:    codec.ClockRate,
-					Channels:     codec.Channels,
-					SDPFmtpLine:  codec.SDPFmtpLine,
-					RTCPFeedback: fb,
-				},
-				PayloadType: ptpe,
-			},
-			tpe,
-		)
 		if err != nil {
 			log.Printf("%v", err)
 			continue
@@ -290,14 +343,14 @@ func APIFromNames(names []string) (*webrtc.API, error) {
 	if len(names) == 0 {
 		names = []string{"vp8", "opus"}
 	}
-	codecs := make([]webrtc.RTPCodecCapability, 0, len(names))
+	var codecs []webrtc.RTPCodecParameters
 	for _, n := range names {
-		codec, err := codecFromName(n)
+		cs, err := codecsFromName(n)
 		if err != nil {
 			log.Printf("Codec %v: %v", n, err)
 			continue
 		}
-		codecs = append(codecs, codec)
+		codecs = append(codecs, cs...)
 	}
 
 	return APIFromCodecs(codecs)

group/group_test.go

@@ -237,3 +237,29 @@ func TestPermissions(t *testing.T) {
 	}
 
 }
+
+func TestFmtpValue(t *testing.T) {
+	type fmtpTest struct {
+		fmtp  string
+		key   string
+		value string
+	}
+	fmtpTests := []fmtpTest{
+		{"", "foo", ""},
+		{"profile-id=0", "profile-id", "0"},
+		{"profile-id=0", "foo", ""},
+		{"level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f", "profile-level-id", "42001f"},
+		{"foo=1;bar=2;quux=3", "foo", "1"},
+		{"foo=1;bar=2;quux=3", "bar", "2"},
+		{"foo=1;bar=2;quux=3", "fu", ""},
+	}
+
+	for _, test := range fmtpTests {
+		v := fmtpValue(test.fmtp, test.key)
+		if v != test.value {
+			t.Errorf("fmtpValue(%v, %v) = %v, expected %v",
+				test.fmtp, test.key, v, test.value,
+			)
+		}
+	}
+}

rtpconn/webclient.go

@@ -389,6 +389,26 @@ func addDownTrackUnlocked(conn *rtpDownConnection, remoteTrack *rtpUpTrack, remo
 		return err
 	}
 
+	codec := local.Codec()
+	ptype, err := group.CodecPayloadType(local.Codec())
+	if err != nil {
+		log.Printf("Couldn't determine ptype for codec %v: %v",
+			codec.MimeType, err)
+	} else {
+		err := transceiver.SetCodecPreferences(
+			[]webrtc.RTPCodecParameters{
+				{
+					RTPCodecCapability: codec,
+					PayloadType:        ptype,
+				},
+			},
+		)
+		if err != nil {
+			log.Printf("Couldn't set ptype for codec %v: %v",
+				codec.MimeType, err)
+		}
+	}
+
 	parms := transceiver.Sender().GetParameters()
 	if len(parms.Encodings) != 1 {
 		return errors.New("got multiple encodings")