rtp: using static memory to hold bytes of rtp pkts

stream/rtp/encoder.go

@@ -40,7 +40,7 @@ const (
 	timestampFreq  = 90000 // Hz
 	mtsSize        = 188
 	bufferSize     = 1000
-	sendLength     = 7 * 188
+	sendLen        = 7 * 188
 )
 
 // Encoder implements io writer and provides functionality to wrap data into
@@ -53,6 +53,7 @@ type Encoder struct {
 	frameInterval time.Duration
 	fps           int
 	buffer        []byte
+	pktSpace      [defPktLen]byte
 }
 
 // NewEncoder returns a new Encoder type given an io.Writer - the destination
@@ -71,9 +72,9 @@ func NewEncoder(dst io.Writer, fps int) *Encoder {
 // so that multiple layers of packetization can occur.
 func (e *Encoder) Write(data []byte) (int, error) {
 	e.buffer = append(e.buffer, data...)
-	for len(e.buffer) >= sendLength {
+	for len(e.buffer) >= sendLen {
-		e.Encode(e.buffer[:sendLength])
+		e.Encode(e.buffer[:sendLen])
-		e.buffer = e.buffer[sendLength:]
+		e.buffer = e.buffer[sendLen:]
 	}
 	return len(data), nil
 }
@@ -93,7 +94,7 @@ func (e *Encoder) Encode(payload []byte) error {
 		Payload: payload,
 		Padding: no,
 	}
-	_, err := e.dst.Write(pkt.Bytes())
+	_, err := e.dst.Write(pkt.Bytes(e.pktSpace[:defPktLen]))
 	if err != nil {
 		return err
 	}

stream/rtp/rtp.go

@@ -34,6 +34,9 @@ package rtp
 
 const (
 	rtpVer        = 2
+	headLen       = 3 * 4
+	defPayloadLen = 7 * 188
+	defPktLen     = headLen + defPayloadLen
 )
 
 // Pkt provides fields consistent with RFC3550 definition of an rtp packet
@@ -53,7 +56,11 @@ type Pkt struct {
 }
 
 // Bytes provides a byte slice of the packet
-func (p *Pkt) Bytes() []byte {
+func (p *Pkt) Bytes(buf []byte) []byte {
+	if buf == nil || len(buf) != defPktLen {
+		buf = make([]byte, headLen, defPktLen)
+	}
+	buf = buf[:headLen]
 	if p.V == 0 {
 		p.V = rtpVer
 	}
@@ -74,9 +81,6 @@ func (p *Pkt) Bytes() []byte {
 		panic("rtp: CC (CSRC count) not 0, but CSRC headers not yet supported.")
 	}
 
-	const headSize = 3 * 4 // bytes
-	buf := make([]byte, headSize, headSize+len(p.Payload)+int(p.Padding))
-
 	buf[0] = p.V<<6 | p.p<<5 | p.CC
 	buf[1] = p.M<<7 | p.PT
 	buf[2] = byte(p.SN >> 8)

stream/rtp/rtp_test.go

@@ -65,7 +65,7 @@ var rtpTests = []struct {
 
 func TestRtpPktToByteSlice(t *testing.T) {
 	for _, test := range rtpTests {
-		got := test.pkt.Bytes()
+		got := test.pkt.Bytes(nil)
 		if !reflect.DeepEqual(got, test.want) {
 			t.Errorf("unexpected error for test %v: got:%v want:%v", test.num, got,
 				test.want)