/// <summary>
/// Handling packets received on the RTP socket. One of the simplest, if not the simplest, cases is
/// PCMU audio packets. THe handling can get substantially more complicated if the RTP socket is being
/// used to multiplex different protocols. This is what WebRTC does with STUN, RTP and RTCP.
/// </summary>
/// <param name="rtpSocket">The raw RTP socket.</param>
/// <param name="rtpSendSession">The session infor for the RTP pakcets being sent.</param>
private static async void RecvRtp(Socket rtpSocket, RTPSession rtpRecvSession, CancellationTokenSource cts)
{
try
{
DateTime lastRecvReportAt = DateTime.Now;
uint packetReceivedCount = 0;
uint bytesReceivedCount = 0;
byte[] buffer = new byte[512];
IPEndPoint anyEndPoint = new IPEndPoint((rtpSocket.AddressFamily == AddressFamily.InterNetworkV6) ? IPAddress.IPv6Any : IPAddress.Any, 0);
Log.LogDebug($"Listening on RTP socket {rtpSocket.LocalEndPoint}.");
using (var waveOutEvent = new WaveOutEvent())
{
var waveProvider = new BufferedWaveProvider(new WaveFormat(8000, 16, 1));
waveProvider.DiscardOnBufferOverflow = true;
waveOutEvent.Init(waveProvider);
waveOutEvent.Play();
var recvResult = await rtpSocket.ReceiveFromAsync(buffer, SocketFlags.None, anyEndPoint);
Log.LogDebug($"Initial RTP packet recieved from {recvResult.RemoteEndPoint}.");
while (recvResult.ReceivedBytes > 0 && !cts.IsCancellationRequested)
{
var rtpPacket = rtpRecvSession.RtpReceive(buffer, 0, recvResult.ReceivedBytes, recvResult.RemoteEndPoint as IPEndPoint);
packetReceivedCount++;
bytesReceivedCount += (uint)rtpPacket.Payload.Length;
for (int index = 0; index < rtpPacket.Payload.Length; index++)
{
short pcm = NAudio.Codecs.MuLawDecoder.MuLawToLinearSample(rtpPacket.Payload[index]);
byte[] pcmSample = new byte[] { (byte)(pcm & 0xFF), (byte)(pcm >> 8) };
waveProvider.AddSamples(pcmSample, 0, 2);
}
if (DateTime.Now.Subtract(lastRecvReportAt).TotalSeconds > RTP_REPORTING_PERIOD_SECONDS)
{
// This is typically where RTCP receiver (RR) reports would be sent. Omitted here for brevity.
lastRecvReportAt = DateTime.Now;
var remoteRtpEndPoint = recvResult.RemoteEndPoint as IPEndPoint;
Log.LogDebug($"RTP recv report {rtpSocket.LocalEndPoint}<-{remoteRtpEndPoint} pkts {packetReceivedCount} bytes {bytesReceivedCount}");
}
recvResult = await rtpSocket.ReceiveFromAsync(buffer, SocketFlags.None, anyEndPoint);
}
}
}
catch (ObjectDisposedException) { } // This is how .Net deals with an in use socket being closed. Safe to ignore.
catch (Exception excp)
{
Log.LogError($"Exception processing RTP. {excp}");
}
}