Add padding support to Packetizer

To add padding-only samples call GeneratePadding

Author: Alex Pokotilo

Diff for: packetizer.go

@@ -15,6 +15,7 @@ type Payloader interface {
 // Packetizer packetizes a payload
 type Packetizer interface {
 	Packetize(payload []byte, samples uint32) []*Packet
+	GeneratePadding(samples uint32) []*Packet
 	EnableAbsSendTime(value int)
 	SkipSamples(skippedSamples uint32)
 }
@@ -98,6 +99,38 @@ func (p *packetizer) Packetize(payload []byte, samples uint32) []*Packet {
 	return packets
 }
 
+// GeneratePadding returns required padding-only packages
+func (p *packetizer) GeneratePadding(samples uint32) []*Packet {
+	// Guard against an empty payload
+	if samples == 0 {
+		return nil
+	}
+
+	packets := make([]*Packet, samples)
+
+	for i := 0; i < int(samples); i++ {
+		pp := make([]byte, 255)
+		pp[254] = 255
+
+		packets[i] = &Packet{
+			Header: Header{
+				Version:        2,
+				Padding:        true,
+				Extension:      false,
+				Marker:         false,
+				PayloadType:    p.PayloadType,
+				SequenceNumber: p.Sequencer.NextSequenceNumber(),
+				Timestamp:      p.Timestamp, // Use latest timestamp
+				SSRC:           p.SSRC,
+				CSRC:           []uint32{},
+			},
+			Payload: pp,
+		}
+	}
+
+	return packets
+}
+
 // SkipSamples causes a gap in sample count between Packetize requests so the
 // RTP payloads produced have a gap in timestamps
 func (p *packetizer) SkipSamples(skippedSamples uint32) {