A C# library to handle RTSP connections.
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STEP 1 - Open TCP Socket connection to the RTSP Server
// Connect to a RTSP Server tcp_socket = new Rtsp.RtspTcpTransport(host,port); if (tcp_socket.Connected == false) { Console.WriteLine("Error - did not connect"); return; }
This opens a connection for a 'TCP' mode RTSP/RTP session where RTP packets are set in the RTSP socket.
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STEP 2 - Create a RTSP Listener and attach it to the RTSP TCP Socket
// Connect a RTSP Listener to the TCP Socket to send messages and listen for replies rtsp_client = new Rtsp.RtspListener(tcp_socket); rtsp_client.MessageReceived += Rtsp_client_MessageReceived; rtsp_client.DataReceived += Rtsp_client_DataReceived; rtsp_client.Start(); // start reading messages from the server
The RTSP Listener class lets you SEND messages to the RTSP Server (see below).
The RTSP Listner class has a worker thread that listens for replies from the RTSP Server.
When replies are received the MessageReceived Event is fired.
When RTP packets are received the DataReceived Event is fired. -
STEP 3 - Send Messages to the RTSP Server
The samples below show how to send messages.
Send OPTIONS with this code :
Rtsp.Messages.RtspRequest options_message = new Rtsp. Messages.RtspRequestOptions(); options_message.RtspUri = new Uri(url); rtsp_client.SendMessage(options_message);
Send DESCRIBE with this code :
```C#
// send the Describe
Rtsp.Messages.RtspRequest describe_message = new Rtsp.Messages.RtspRequestDescribe();
describe_message.RtspUri = new Uri(url);
rtsp_client.SendMessage(describe_message);
// The reply will include the SDP data
Send SETUP with this code :
// the value of 'control' comes from parsing the SDP for the desired video or audio sub-stream
Rtsp.Messages.RtspRequest setup_message = new Rtsp.Messages.RtspRequestSetup();
setup_message.RtspUri = new Uri(url + "/" + control);
setup_message.AddHeader("Transport: RTP/AVP/TCP;interleaved=0");
rtsp_client.SendMessage(setup_message);
// The reply will include the SessionSend PLAY with this code :
// the value of 'session' comes from the reply of the SETUP command
Rtsp.Messages.RtspRequest play_message = new Rtsp.Messages.RtspRequestPlay();
play_message.RtspUri = new Uri(url);
play_message.Session = session;
rtsp_client.SendMessage(play_message);-
STEP 4 - Handle Replies when the MessageReceived event is fired
This example assumes the main program sends an OPTIONS Command.
It looks for a reply from the server for OPTIONS and then sends DESCRIBE.
It looks for a reply from the server for DESCRIBE and then sends SETUP (for the video stream)
It looks for a reply from the server for SETUP and then sends PLAY.
Once PLAY has been sent the video, in the form of RTP packets, will be received.private void Rtsp_client_MessageReceived(object sender, Rtsp.RtspChunkEventArgs e) { Rtsp.Messages.RtspResponse message = e.Message as Rtsp.Messages.RtspResponse; Console.WriteLine("Received " + message.OriginalRequest.ToString()); if (message.OriginalRequest != null && message.OriginalRequest is Rtsp.Messages.RtspRequestOptions) { // send the DESCRIBE Rtsp.Messages.RtspRequest describe_message = new Rtsp.Messages.RtspRequestDescribe(); describe_message.RtspUri = new Uri(url); rtsp_client.SendMessage(describe_message); } if (message.OriginalRequest != null && message.OriginalRequest is Rtsp.Messages.RtspRequestDescribe) { // Got a reply for DESCRIBE // Examine the SDP Console.Write(System.Text.Encoding.UTF8.GetString(message.Data)); Rtsp.Sdp.SdpFile sdp_data; using (StreamReader sdp_stream = new StreamReader(new MemoryStream(message.Data))) { sdp_data = Rtsp.Sdp.SdpFile.Read(sdp_stream); } // Process each 'Media' Attribute in the SDP. // If the attribute is for Video, then send a SETUP for (int x = 0; x < sdp_data.Medias.Count; x++) { if (sdp_data.Medias[x].GetMediaType() == Rtsp.Sdp.Media.MediaType.video) { // seach the atributes for control, fmtp and rtpmap String control = ""; // the "track" or "stream id" String fmtp = ""; // holds SPS and PPS String rtpmap = ""; // holds the Payload format, 96 is often used with H264 foreach (Rtsp.Sdp.Attribut attrib in sdp_data.Medias[x].Attributs) { if (attrib.Key.Equals("control")) control = attrib.Value; if (attrib.Key.Equals("fmtp")) fmtp = attrib.Value; if (attrib.Key.Equals("rtpmap")) rtpmap = attrib.Value; } // Get the Payload format number for the Video Stream String[] split_rtpmap = rtpmap.Split(' '); video_payload = 0; bool result = Int32.TryParse(split_rtpmap[0], out video_payload); // Send SETUP for the Video Stream // using Interleaved mode (RTP frames over the RTSP socket) Rtsp.Messages.RtspRequest setup_message = new Rtsp.Messages.RtspRequestSetup(); setup_message.RtspUri = new Uri(url + "/" + control); setup_message.AddHeader("Transport: RTP/AVP/TCP;interleaved=0"); rtsp_client.SendMessage(setup_message); } } } if (message.OriginalRequest != null && message.OriginalRequest is Rtsp.Messages.RtspRequestSetup) { // Got Reply to SETUP Console.WriteLine("Got reply from Setup. Session is " + message.Session); String session = message.Session; // Session value used with Play, Pause, Teardown // Send PLAY Rtsp.Messages.RtspRequest play_message = new Rtsp.Messages.RtspRequestPlay(); play_message.RtspUri = new Uri(url); play_message.Session = session; rtsp_client.SendMessage(play_message); } if (message.OriginalRequest != null && message.OriginalRequest is Rtsp.Messages.RtspRequestPlay) { // Got Reply to PLAY Console.WriteLine("Got reply from Play " + message.Command); } }
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STEP 5 - Handle RTP Video
This code handles each incoming RTP packet, combining RTP packets that are all part of the same frame of vdeo (using the Marker Bit). Once a full frame is received it can be passed to a De-packetiser to get the compressed video data
List<byte[]> temporary_rtp_payloads = new List<byte[]>(); private void Rtsp_client_DataReceived(object sender, Rtsp.RtspChunkEventArgs e) { // RTP Packet Header // 0 - Version, P, X, CC, M, PT and Sequence Number //32 - Timestamp //64 - SSRC //96 - CSRCs (optional) //nn - Extension ID and Length //nn - Extension header int rtp_version = (e.Message.Data[0] >> 6); int rtp_padding = (e.Message.Data[0] >> 5) & 0x01; int rtp_extension = (e.Message.Data[0] >> 4) & 0x01; int rtp_csrc_count = (e.Message.Data[0] >> 0) & 0x0F; int rtp_marker = (e.Message.Data[1] >> 7) & 0x01; int rtp_payload_type = (e.Message.Data[1] >> 0) & 0x7F; uint rtp_sequence_number = ((uint)e.Message.Data[2] << 8) + (uint)(e.Message.Data[3]); uint rtp_timestamp = ((uint)e.Message.Data[4] <<24) + (uint)(e.Message.Data[5] << 16) + (uint)(e.Message.Data[6] << 8) + (uint)(e.Message.Data[7]); uint rtp_ssrc = ((uint)e.Message.Data[8] << 24) + (uint)(e.Message.Data[9] << 16) + (uint)(e.Message.Data[10] << 8) + (uint)(e.Message.Data[11]); int rtp_payload_start = 4 // V,P,M,SEQ + 4 // time stamp + 4 // ssrc + (4 * rtp_csrc_count); // zero or more csrcs uint rtp_extension_id = 0; uint rtp_extension_size = 0; if (rtp_extension == 1) { rtp_extension_id = ((uint)e.Message.Data[rtp_payload_start + 0] << 8) + (uint)(e.Message.Data[rtp_payload_start + 1] << 0); rtp_extension_size = ((uint)e.Message.Data[rtp_payload_start + 2] << 8) + (uint)(e.Message.Data[rtp_payload_start + 3] << 0); rtp_payload_start += 4 + (int)rtp_extension_size; // extension header and extension payload } Console.WriteLine("RTP Data" + " V=" + rtp_version + " P=" + rtp_padding + " X=" + rtp_extension + " CC=" + rtp_csrc_count + " M=" + rtp_marker + " PT=" + rtp_payload_type + " Seq=" + rtp_sequence_number + " Time=" + rtp_timestamp + " SSRC=" + rtp_ssrc + " Size=" + e.Message.Data.Length); if (rtp_payload_type != video_payload) { Console.WriteLine("Ignoring this RTP payload"); return; // ignore this data } // If rtp_marker is '1' then this is the final transmission for this packet. // If rtp_marker is '0' we need to accumulate data with the same timestamp // ToDo - Check Timestamp matches // Add to the tempoary_rtp List byte[] rtp_payload = new byte[e.Message.Data.Length - rtp_payload_start]; // payload with RTP header removed System.Array.Copy(e.Message.Data, rtp_payload_start, rtp_payload, 0, rtp_payload.Length); // copy payload temporary_rtp_payloads.Add(rtp_payload); if (rtp_marker == 1) { // Process the RTP frame Process_RTP_Frame(temporary_rtp_payloads); temporary_rtp_payloads.Clear(); } }
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STEP 6 - Process RTP frame
An RTP frame consists of 1 or more RTP packets
H264 video is packed into one or more RTP packets and this sample extracts Normal Packing and Fragmented Unit type A packing (the common two)
This example writes the video to a .264 file which can be played with FFPLAYFileStream fs = null; byte[] nal_header = new byte[]{ 0x00, 0x00, 0x00, 0x01 }; int norm, fu_a, fu_b, stap_a, stap_b, mtap16, mtap24 = 0; // stats counters public void Process_RTP_Frame(List<byte[]>rtp_payloads) { Console.WriteLine("RTP Data comprised of " + rtp_payloads.Count + " rtp packets"); if (fs == null) { // Create the file String filename = "rtsp_capture_" + DateTime.Now.ToString("yyyyMMdd_HHmmss") + ".h264"; fs = new FileStream(filename, FileMode.Create); // TODO. Get SPS and PPS from the SDP Attributes (the fmtp attribute) and write to the file // for IP cameras that only out the SPS and PPS out-of-band } for (int payload_index = 0; payload_index < rtp_payloads.Count; payload_index++) { // Examine the first rtp_payload and the first byte (the NAL header) int nal_header_f_bit = (rtp_payloads[payload_index][0] >> 7) & 0x01; int nal_header_nri = (rtp_payloads[payload_index][0] >> 5) & 0x03; int nal_header_type = (rtp_payloads[payload_index][0] >> 0) & 0x1F; // If the NAL Header Type is in the range 1..23 this is a normal NAL (not fragmented) // So write the NAL to the file if (nal_header_type >= 1 && nal_header_type <= 23) { Console.WriteLine("Normal NAL"); norm++; fs.Write(nal_header, 0, nal_header.Length); fs.Write(rtp_payloads[payload_index], 0, rtp_payloads[payload_index].Length); } else if (nal_header_type == 24) { // There are 4 types of Aggregation Packet (multiple NALs in one RTP packet) Console.WriteLine("Agg STAP-A not supported"); stap_a++; } else if (nal_header_type == 25) { // There are 4 types of Aggregation Packet (multiple NALs in one RTP packet) Console.WriteLine("Agg STAP-B not supported"); stap_b++; } else if (nal_header_type == 26) { // There are 4 types of Aggregation Packet (multiple NALs in one RTP packet) Console.WriteLine("Agg MTAP16 not supported"); mtap16++; } else if (nal_header_type == 27) { // There are 4 types of Aggregation Packet (multiple NALs in one RTP packet) Console.WriteLine("Agg MTAP24 not supported"); mtap24++; } else if (nal_header_type == 28) { Console.WriteLine("Fragmented Packet Type FU-A"); fu_a++; // Parse Fragmentation Unit Header int fu_header_s = (rtp_payloads[payload_index][1] >> 7) & 0x01; // start marker int fu_header_e = (rtp_payloads[payload_index][1] >> 6) & 0x01; // end marker int fu_header_r = (rtp_payloads[payload_index][1] >> 5) & 0x01; // reserved. should be 0 int fu_header_type = (rtp_payloads[payload_index][1] >> 0) & 0x1F; // Original NAL unit header Console.WriteLine("Frag FU-A s="+fu_header_s + "e="+fu_header_e); // Start Flag set if (fu_header_s == 1) { // Write 00 00 00 01 header fs.Write(nal_header, 0, nal_header.Length); // 0x00 0x00 0x00 0x01 // Modify the NAL Header that was at the start of the RTP packet // Keep the F and NRI flags but substitute the type field with the fu_header_type byte reconstructed_nal_type = (byte)((nal_header_nri << 5) + fu_header_type); fs.WriteByte(reconstructed_nal_type); // NAL Unit Type fs.Write(rtp_payloads[payload_index], 2, rtp_payloads[payload_index].Length - 2); // start after NAL Unit Type and FU Header byte } if (fu_header_s == 0) { // append this payload to the output NAL stream // Data starts after the NAL Unit Type byte and the FU Header byte fs.Write(rtp_payloads[payload_index], 2, rtp_payloads[payload_index].Length-2); // start after NAL Unit Type and FU Header byte } } else if (nal_header_type == 29) { Console.WriteLine("Fragmented Packet FU-B not supported"); fu_b++; } else { Console.WriteLine("Unknown NAL header " + nal_header_type); } } // ensure video is written to disk fs.Flush(true); // Print totals Console.WriteLine("Norm=" + norm + " ST-A=" + stap_a + " ST-B=" + stap_b + " M16=" + mtap16 + " M24=" + mtap24 + " FU-A=" + fu_a + " FU-B=" + fu_b); }