rtmp: fix timestamp conversion from RTSP/HLS to RTMP (#1899)

this was causing moments of silence and timing errors when reading with
RTMP a stream originally published with RTSP or HLS.

internal/rtmp/rawmessage/writer.go

@@ -14,8 +14,8 @@ type writerChunkStream struct {
 	lastMessageStreamID *uint32
 	lastType            *uint8
 	lastBodyLen         *uint32
-	lastTimestamp       *time.Duration
-	lastTimestampDelta  *time.Duration
+	lastTimestamp       *int64
+	lastTimestampDelta  *int64
 }
 
 func (wc *writerChunkStream) writeChunk(c chunk.Chunk) error {
@@ -46,9 +46,13 @@ func (wc *writerChunkStream) writeMessage(msg *Message) error {
 	pos := uint32(0)
 	firstChunk := true
 
-	var timestampDelta *time.Duration
+	// convert timestamp to milliseconds before splitting message in chunks
+	/// otherwise timestampDelta gets messed up.
+	timestamp := int64(msg.Timestamp / time.Millisecond)
+
+	var timestampDelta *int64
 	if wc.lastTimestamp != nil {
-		diff := msg.Timestamp - *wc.lastTimestamp
+		diff := timestamp - *wc.lastTimestamp
 
 		// use delta only if it is positive
 		if diff >= 0 {
@@ -69,7 +73,7 @@ func (wc *writerChunkStream) writeMessage(msg *Message) error {
 			case wc.lastMessageStreamID == nil || timestampDelta == nil || *wc.lastMessageStreamID != msg.MessageStreamID:
 				err := wc.writeChunk(&chunk.Chunk0{
 					ChunkStreamID:   msg.ChunkStreamID,
-					Timestamp:       uint32(msg.Timestamp / time.Millisecond),
+					Timestamp:       uint32(timestamp),
 					Type:            msg.Type,
 					MessageStreamID: msg.MessageStreamID,
 					BodyLen:         (bodyLen),
@@ -82,7 +86,7 @@ func (wc *writerChunkStream) writeMessage(msg *Message) error {
 			case *wc.lastType != msg.Type || *wc.lastBodyLen != bodyLen:
 				err := wc.writeChunk(&chunk.Chunk1{
 					ChunkStreamID:  msg.ChunkStreamID,
-					TimestampDelta: uint32(*timestampDelta / time.Millisecond),
+					TimestampDelta: uint32(*timestampDelta),
 					Type:           msg.Type,
 					BodyLen:        (bodyLen),
 					Body:           msg.Body[pos : pos+chunkBodyLen],
@@ -94,7 +98,7 @@ func (wc *writerChunkStream) writeMessage(msg *Message) error {
 			case wc.lastTimestampDelta == nil || *wc.lastTimestampDelta != *timestampDelta:
 				err := wc.writeChunk(&chunk.Chunk2{
 					ChunkStreamID:  msg.ChunkStreamID,
-					TimestampDelta: uint32(*timestampDelta / time.Millisecond),
+					TimestampDelta: uint32(*timestampDelta),
 					Body:           msg.Body[pos : pos+chunkBodyLen],
 				})
 				if err != nil {
@@ -117,7 +121,7 @@ func (wc *writerChunkStream) writeMessage(msg *Message) error {
 			wc.lastType = &v2
 			v3 := bodyLen
 			wc.lastBodyLen = &v3
-			v4 := msg.Timestamp
+			v4 := timestamp
 			wc.lastTimestamp = &v4
 
 			if timestampDelta != nil {