codec/h265: fixed lexer to get nal header into start of fragment

Now getting the nal header and type from fu header for the first fragment. We can now
lex and create HEVC MTS to RTP - working fine. Need to use RTCP now to continue stream.

codec/h265/lex.go

@@ -76,6 +76,7 @@ func (l *Lexer) Lex(dst io.Writer, src io.Reader, delay time.Duration) error {
 		switch err {
 		case nil: // Do nothing.
 		case io.EOF:
+			fmt.Println("done")
 			return nil
 		default:
 			return fmt.Errorf("source read error: %v\n", err)
@@ -150,6 +151,11 @@ func (l *Lexer) handleFragmentation(d []byte) {
 	start := d[2]&0x80 != 0
 	end := d[2]&0x40 != 0
 
+	var head []byte
+	if start {
+		head = []byte{(d[0] & 0x81) | ((d[2] & 0x3f) << 1), d[1]}
+	}
+
 	d = d[3:]
 	if l.donl {
 		d = d[2:]
@@ -158,7 +164,8 @@ func (l *Lexer) handleFragmentation(d []byte) {
 	switch {
 	case start && !end:
 		l.frag = true
-		l.writeWithPrefix(d)
+		_d := append(head, d...)
+		l.writeWithPrefix(_d)
 	case !start && end:
 		l.frag = false
 		fallthrough