private static SDP GetSDP(IPEndPoint rtpSocket, RTPPayloadTypesEnum audioPayloadType)
{
int samplingFrequency = RTPPayloadTypes.GetSamplingFrequency(audioPayloadType);
var sdp = new SDP()
{
SessionId = Crypto.GetRandomInt(5).ToString(),
Address = rtpSocket.Address.ToString(),
SessionName = "sipsorcery",
Timing = "0 0",
Connection = new SDPConnectionInformation(rtpSocket.Address.ToString()),
};
var audioAnnouncement = new SDPMediaAnnouncement()
{
Media = SDPMediaTypesEnum.audio,
MediaFormats = new List <SDPMediaFormat>()
{
new SDPMediaFormat((int)audioPayloadType, "PCMU", samplingFrequency)
}
};
audioAnnouncement.Port = rtpSocket.Port;
audioAnnouncement.ExtraAttributes.Add("a=sendrecv");
audioAnnouncement.ExtraAttributes.Add($"a=rtpmap:{DTMF_EVENT_PAYLOAD_ID} telephone-event/{samplingFrequency}");
audioAnnouncement.ExtraAttributes.Add($"a=fmtp:{DTMF_EVENT_PAYLOAD_ID} 0-15");
sdp.Media.Add(audioAnnouncement);
return(sdp);
}
/// <summary>
/// Sends the sounds of silence. If the destination is on the other side of a NAT this is useful to open
/// a pinhole and hopefully get the remote RTP stream through.
/// </summary>
/// <param name="rtpSocket">The socket we're using to send from.</param>
/// <param name="rtpSendSession">Our RTP sending session.</param>
/// <param name="cts">Cancellation token to stop the call.</param>
private static async void SendRtp(Socket rtpSocket, RTPSession rtpSendSession, CancellationTokenSource cts)
{
int samplingFrequency = RTPPayloadTypes.GetSamplingFrequency((RTPPayloadTypesEnum)rtpSendSession.PayloadType);
uint rtpTimestampStep = (uint)(samplingFrequency * SILENCE_SAMPLE_PERIOD / 1000);
uint bufferSize = (uint)SILENCE_SAMPLE_PERIOD;
uint rtpSendTimestamp = 0;
uint packetSentCount = 0;
uint bytesSentCount = 0;
while (cts.IsCancellationRequested == false)
{
if (_remoteRtpEndPoint != null)
{
if (!_dtmfEvents.IsEmpty)
{
// Check if there are any DTMF events to send.
_dtmfEvents.TryDequeue(out var rtpEvent);
if (rtpEvent != null)
{
await rtpSendSession.SendDtmfEvent(rtpSocket, _remoteRtpEndPoint, rtpEvent, rtpSendTimestamp, (ushort)SILENCE_SAMPLE_PERIOD, (ushort)rtpTimestampStep, cts);
}
rtpSendTimestamp += rtpEvent.TotalDuration + rtpTimestampStep;
}
else
{
// If there are no DTMF events to send we'll send silence.
byte[] sample = new byte[bufferSize / 2];
int sampleIndex = 0;
for (int index = 0; index < bufferSize; index += 2)
{
sample[sampleIndex] = PCMU_SILENCE_BYTE_ZERO;
sample[sampleIndex + 1] = PCMU_SILENCE_BYTE_ONE;
}
rtpSendSession.SendAudioFrame(rtpSocket, _remoteRtpEndPoint, rtpSendTimestamp, sample);
rtpSendTimestamp += rtpTimestampStep;
packetSentCount++;
bytesSentCount += (uint)sample.Length;
}
}
await Task.Delay(SILENCE_SAMPLE_PERIOD);
}
}