Decode streams once and only when needed (#1218)

* split data into specialized structs

* move MPEG4-audio decoding into streamTrack

* restore video/audio synchronization in HLS muxer and RTMP server

* log decode errors

* move H264 decoding and re-encoding here from gortsplib

* add tests

* update gortsplib

internal/core/rpicamera_source.go

@@ -59,12 +59,15 @@ func (s *rpiCameraSource) run(ctx context.Context) error {
 			stream = res.stream
 		}
 
-		stream.writeData(&data{
+		err := stream.writeData(&dataH264{
 			trackID:      0,
 			ptsEqualsDTS: h264.IDRPresent(nalus),
 			pts:          dts,
-			h264NALUs:    nalus,
+			nalus:        nalus,
 		})
+		if err != nil {
+			s.Log(logger.Warn, "%v", err)
+		}
 	}
 
 	cam, err := rpicamera.New(s.params, onData)