Add additional helper methods for the jitter buffer

pkg/jitterbuffer/jitter_buffer.go

@@ -186,6 +186,39 @@ func (jb *JitterBuffer) Pop() (*rtp.Packet, error) {
 	return packet, nil
 }
 
+// Pop an RTP packet from the jitter buffer at the specified Sequence
+func (jb *JitterBuffer) PopAtSequence(sq uint16) (*rtp.Packet, error) {
+	jb.mutex.Lock()
+	defer jb.mutex.Unlock()
+	if jb.state != Emitting {
+		return nil, ErrPopWhileBuffering
+	}
+	packet, err := jb.packets.PopAt(sq)
+	if err != nil {
+		jb.stats.underflowCount++
+		jb.emit(BufferUnderflow)
+		return (*rtp.Packet)(nil), err
+	}
+	jb.playoutHead = (jb.playoutHead + 1) % math.MaxUint16
+	jb.updateState()
+	return packet, nil
+}
+
+// Peek an RTP packet from the jitter buffer at the specified Sequence
+func (jb *JitterBuffer) PeekAtSequence(sq uint16) (*rtp.Packet, error) {
+	jb.mutex.Lock()
+	defer jb.mutex.Unlock()
+	if jb.state != Emitting {
+		return nil, ErrPopWhileBuffering
+	}
+	packet, err := jb.packets.Find(sq)
+	if err != nil {
+		return (*rtp.Packet)(nil), err
+	}
+	return packet, nil
+}
+
+
 // PopAtTimestamp pops an RTP packet from the jitter buffer with the provided timestamp
 // Call this method repeatedly to drain the buffer at the timestamp
 func (jb *JitterBuffer) PopAtTimestamp(ts uint32) (*rtp.Packet, error) {