add RTP/VP9 encoder and decoder (#152)

examples/client-read-codec-vp8/main.go

@@ -36,15 +36,15 @@ func main() {
 	}
 
 	// find the VP8 track
-	vp8Track, vp8TrackID := func() (*gortsplib.TrackVP8, int) {
-		for i, track := range tracks {
+	track := func() *gortsplib.TrackVP8 {
+		for _, track := range tracks {
 			if tt, ok := track.(*gortsplib.TrackVP8); ok {
-				return tt, i
+				return tt
 			}
 		}
-		return nil, -1
+		return nil
 	}()
-	if vp8Track == nil {
+	if track == nil {
 		panic("VP8 track not found")
 	}
 
@@ -54,10 +54,6 @@ func main() {
 
 	// called when a RTP packet arrives
 	c.OnPacketRTP = func(ctx *gortsplib.ClientOnPacketRTPCtx) {
-		if ctx.TrackID != vp8TrackID {
-			return
-		}
-
 		// decode a VP8 frame from the RTP packet
 		vf, _, err := dec.Decode(ctx.Packet)
 		if err != nil {
@@ -67,8 +63,8 @@ func main() {
 		log.Printf("received frame of size %d\n", len(vf))
 	}
 
-	// setup and read all tracks
-	err = c.SetupAndPlay(tracks, baseURL)
+	// setup and read the VP8 track only
+	err = c.SetupAndPlay(gortsplib.Tracks{track}, baseURL)
 	if err != nil {
 		panic(err)
 	}