rtmp: fix crash when publishing video-only tracks (#1819) (#1822)

this fixes a regression introduced in v0.23.0.

README.md

@@ -1217,7 +1217,7 @@ For more advanced options, you can create and serve a custom web page by startin
 
 * WebRTC
   * [WebRTC: Real-Time Communication in Browsers](https://www.w3.org/TR/webrtc/)
-  * [WebRTC Ingestion Protocol (WHIP)](https://datatracker.ietf.org/doc/draft-ietf-wish-whip/)
+  * [WebRTC HTTP Ingestion Protocol (WHIP)](https://datatracker.ietf.org/doc/draft-ietf-wish-whip/)
   * [WebRTC HTTP Egress Protocol (WHEP)](https://datatracker.ietf.org/doc/draft-murillo-whep/)
 
 * Video and audio codecs

internal/rtmp/tracks/read.go

@@ -44,7 +44,7 @@ func trackFromH264DecoderConfig(data []byte) (formats.Format, error) {
 	}, nil
 }
 
-func trackFromAACDecoderConfig(data []byte) (*formats.MPEG4Audio, error) {
+func trackFromAACDecoderConfig(data []byte) (formats.Format, error) {
 	var mpegConf mpeg4audio.Config
 	err := mpegConf.Unmarshal(data)
 	if err != nil {
@@ -261,10 +261,10 @@ func readTracksFromMetadata(r *message.ReadWriter, payload []interface{}) (forma
 	}
 }
 
-func readTracksFromMessages(r *message.ReadWriter, msg message.Message) (formats.Format, *formats.MPEG4Audio, error) {
+func readTracksFromMessages(r *message.ReadWriter, msg message.Message) (formats.Format, formats.Format, error) {
 	var startTime *time.Duration
 	var videoTrack formats.Format
-	var audioTrack *formats.MPEG4Audio
+	var audioTrack formats.Format
 
 	// analyze 1 second of packets
 outer:

internal/rtmp/tracks/read_test.go

@@ -63,7 +63,7 @@ func TestRead(t *testing.T) {
 			nil,
 		},
 		{
-			"metadata without codec id",
+			"metadata without codec id, video+audio",
 			&formats.H264{
 				PayloadTyp:        96,
 				SPS:               sps,
@@ -82,6 +82,16 @@ func TestRead(t *testing.T) {
 				IndexDeltaLength: 3,
 			},
 		},
+		{
+			"metadata without codec id, video only",
+			&formats.H264{
+				PayloadTyp:        96,
+				SPS:               sps,
+				PPS:               pps,
+				PacketizationMode: 1,
+			},
+			nil,
+		},
 		{
 			"missing metadata, video+audio",
 			&formats.H264{
@@ -266,7 +276,7 @@ func TestRead(t *testing.T) {
 				})
 				require.NoError(t, err)
 
-			case "metadata without codec id":
+			case "metadata without codec id, video+audio":
 				err := mrw.Write(&message.DataAMF0{
 					ChunkStreamID:   4,
 					MessageStreamID: 1,
@@ -325,6 +335,57 @@ func TestRead(t *testing.T) {
 				})
 				require.NoError(t, err)
 
+			case "metadata without codec id, video only":
+				err := mrw.Write(&message.DataAMF0{
+					ChunkStreamID:   4,
+					MessageStreamID: 1,
+					Payload: []interface{}{
+						"@setDataFrame",
+						"onMetaData",
+						flvio.AMFMap{
+							{
+								K: "width",
+								V: float64(2688),
+							},
+							{
+								K: "height",
+								V: float64(1520),
+							},
+							{
+								K: "framerate",
+								V: float64(0o25),
+							},
+						},
+					},
+				})
+				require.NoError(t, err)
+
+				buf, _ := h264conf.Conf{
+					SPS: sps,
+					PPS: pps,
+				}.Marshal()
+
+				err = mrw.Write(&message.Video{
+					ChunkStreamID:   message.VideoChunkStreamID,
+					MessageStreamID: 0x1000000,
+					Codec:           message.CodecH264,
+					IsKeyFrame:      true,
+					Type:            message.VideoTypeConfig,
+					Payload:         buf,
+				})
+				require.NoError(t, err)
+
+				err = mrw.Write(&message.Video{
+					ChunkStreamID:   message.VideoChunkStreamID,
+					MessageStreamID: 0x1000000,
+					Codec:           message.CodecH264,
+					IsKeyFrame:      true,
+					Type:            message.VideoTypeAU,
+					Payload:         []byte{0x01, 0x02, 0x03, 0x04},
+					DTS:             1 * time.Second,
+				})
+				require.NoError(t, err)
+
 			case "missing metadata, video+audio":
 				buf, _ := h264conf.Conf{
 					SPS: sps,