codec/h265: removed unnecessary allocation in handle fragmentation

codec/h265/lex.go

@@ -63,7 +63,8 @@ type Lexer struct {
 func NewLexer(donl bool) *Lexer {
 	return &Lexer{
 		donl: donl,
-		buf:  bytes.NewBuffer(make([]byte, 0, maxAUSize))}
+		buf:  bytes.NewBuffer(make([]byte, 0, maxAUSize)),
+	}
 }
 
 // Lex continually reads RTP packets from the io.Reader src and lexes into
@@ -150,21 +151,25 @@ func (l *Lexer) handleFragmentation(d []byte) {
 	start := d[2]&0x80 != 0
 	end := d[2]&0x40 != 0
 
-	var head []byte
+	old := d
 	if start {
-		head = []byte{(d[0] & 0x81) | ((d[2] & 0x3f) << 1), d[1]}
+		d = d[1:]
+		if l.donl {
+			d = d[2:]
 		}
-
+		d[0] = (old[0] & 0x81) | ((old[2] & 0x3f) << 1)
+		d[1] = old[1]
+	} else {
 		d = d[3:]
 		if l.donl {
 			d = d[2:]
 		}
+	}
 
 	switch {
 	case start && !end:
 		l.frag = true
-		_d := append(head, d...)
-		l.writeWithPrefix(_d)
+		l.writeWithPrefix(d)
 	case !start && end:
 		l.frag = false
 		fallthrough