fix support for LPCM tracks with no explicit channel count

(bluenviron/mediamtx#1292)

track_lpcm.go

@@ -39,8 +39,8 @@ func newTrackLPCMFromMediaDescription(
 		bitDepth = 24
 	}
 
-	tmp := strings.SplitN(clock, "/", 32)
-	if len(tmp) != 2 {
+	tmp := strings.SplitN(clock, "/", 2)
+	if len(tmp) < 1 {
 		return nil, fmt.Errorf("invalid clock (%v)", clock)
 	}
 
@@ -49,16 +49,22 @@ func newTrackLPCMFromMediaDescription(
 		return nil, err
 	}
 
-	channelCount, err := strconv.ParseInt(tmp[1], 10, 64)
-	if err != nil {
-		return nil, err
+	var channelCount int
+	if len(tmp) >= 2 {
+		tmp, err := strconv.ParseInt(tmp[1], 10, 64)
+		if err != nil {
+			return nil, err
+		}
+		channelCount = int(tmp)
+	} else {
+		channelCount = 1
 	}
 
 	return &TrackLPCM{
 		PayloadType:  payloadType,
 		BitDepth:     bitDepth,
 		SampleRate:   int(sampleRate),
-		ChannelCount: int(channelCount),
+		ChannelCount: channelCount,
 		trackBase: trackBase{
 			control: control,
 		},

track_test.go

@@ -95,6 +95,28 @@ func TestTrackNewFromMediaDescription(t *testing.T) {
 				ChannelCount: 2,
 			},
 		},
+		{
+			"lpcm 16 with no explicit channel",
+			&psdp.MediaDescription{
+				MediaName: psdp.MediaName{
+					Media:   "audio",
+					Protos:  []string{"RTP", "AVP"},
+					Formats: []string{"97"},
+				},
+				Attributes: []psdp.Attribute{
+					{
+						Key:   "rtpmap",
+						Value: "97 L16/16000",
+					},
+				},
+			},
+			&TrackLPCM{
+				PayloadType:  97,
+				BitDepth:     16,
+				SampleRate:   16000,
+				ChannelCount: 1,
+			},
+		},
 		{
 			"lpcm 24",
 			&psdp.MediaDescription{