fix parsing of H264 tracks with empty sprop-parameter-sets

pkg/format/format_test.go

@@ -443,6 +443,30 @@ func TestNewFromMediaDescription(t *testing.T) {
 				PacketizationMode: 1,
 			},
 		},
+		{
+			"h264 empty sprop-parameter-sets",
+			&psdp.MediaDescription{
+				MediaName: psdp.MediaName{
+					Media:   "video",
+					Protos:  []string{"RTP", "AVP"},
+					Formats: []string{"96"},
+				},
+				Attributes: []psdp.Attribute{
+					{
+						Key:   "rtpmap",
+						Value: "96 H264/90000",
+					},
+					{
+						Key:   "fmtp",
+						Value: "96 packetization-mode=1; sprop-parameter-sets=",
+					},
+				},
+			},
+			&H264{
+				PayloadTyp:        96,
+				PacketizationMode: 1,
+			},
+		},
 		{
 			"video h265",
 			&psdp.MediaDescription{

pkg/format/h264.go

@@ -117,23 +117,21 @@ func (t *H264) unmarshal(payloadType uint8, clock string, codec string, rtpmap s
 		switch tmp[0] {
 		case "sprop-parameter-sets":
 			tmp := strings.Split(tmp[1], ",")
-			if len(tmp) < 2 {
-				return fmt.Errorf("invalid sprop-parameter-sets (%v)", fmtp)
-			}
+			if len(tmp) >= 2 {
+				sps, err := base64.StdEncoding.DecodeString(tmp[0])
+				if err != nil {
+					return fmt.Errorf("invalid sprop-parameter-sets (%v)", fmtp)
+				}
 
-			sps, err := base64.StdEncoding.DecodeString(tmp[0])
-			if err != nil {
-				return fmt.Errorf("invalid sprop-parameter-sets (%v)", fmtp)
-			}
+				pps, err := base64.StdEncoding.DecodeString(tmp[1])
+				if err != nil {
+					return fmt.Errorf("invalid sprop-parameter-sets (%v)", fmtp)
+				}
 
-			pps, err := base64.StdEncoding.DecodeString(tmp[1])
-			if err != nil {
-				return fmt.Errorf("invalid sprop-parameter-sets (%v)", fmtp)
+				t.SPS = sps
+				t.PPS = pps
 			}
 
-			t.SPS = sps
-			t.PPS = pps
-
 		case "packetization-mode":
 			tmp, err := strconv.ParseInt(tmp[1], 10, 64)
 			if err != nil {