Fix codec negotiation when mono channel is set explicitly. (#300)

Author: dennwc

pkg/media/sdp/codecs.go

@@ -28,7 +28,11 @@ func init() {
 	media.OnRegister(func(c media.Codec) {
 		name := c.Info().SDPName
 		if name != "" {
-			codecByName[strings.ToLower(name)] = c
+			name = strings.ToLower(name)
+			codecByName[name] = c
+			if strings.Count(name, "/") == 1 {
+				codecByName[name+"/1"] = c
+			}
 		}
 	})
 }

pkg/media/sdp/offer.go

@@ -306,7 +306,7 @@ func ParseMedia(d *sdp.MediaDescription) (*MediaDesc, error) {
 				continue
 			}
 			name := sub[1]
-			if name == dtmf.SDPName {
+			if name == dtmf.SDPName || name == dtmf.SDPName+"/1" {
 				out.DTMFType = byte(typ)
 				continue
 			}

pkg/media/sdp/offer_test.go

@@ -214,6 +214,20 @@ func TestSDPMediaAnswer(t *testing.T) {
 				DTMFType: 101,
 			},
 		},
+		{
+			name: "explicit mono channel",
+			offer: sdp.MediaDescription{
+				Attributes: []sdp.Attribute{
+					{Key: "rtpmap", Value: "0 PCMU/8000/1"},
+					{Key: "rtpmap", Value: "101 telephone-event/8000/1"},
+				},
+			},
+			exp: &AudioConfig{
+				Codec:    getCodec(g711.ULawSDPName),
+				Type:     0,
+				DTMFType: 101,
+			},
+		},
 	}
 	for _, c := range cases {
 		c := c