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• RTP packets detected as UDP

  8 juillet 2024, par fritz

  Here is what I am trying to do :

  



  WebRTC endpoint > RTP Endpoint > ffmpeg > RTMP server.


  



  This is what my SDP file looks like.

  



  var cm_offer = "v=0\n" +
              "o=- 3641290734 3641290734 IN IP4 127.0.0.1\n" +
              "s=nginx\n" +
              "c=IN IP4 127.0.0.1\n" +
              "t=0 0\n" +
              "m=audio 60820 RTP/AVP 0\n" +
              "a=rtpmap:0 PCMU/8000\n" +
              "a=recvonly\n" +
              "m=video 59618 RTP/AVP 101\n" +
              "a=rtpmap:101 H264/90000\n" +
              "a=recvonly\n";


  



  What's happening is that wireshark can detect the incoming packets at port 59618, but not as RTP packets but UDP packets. I am trying to capture the packets using ffmpeg with the following command :

  



  ubuntu@ip-132-31-40-100:~$ ffmpeg -i udp://127.0.0.1:59618 -vcodec copy stream.mp4
ffmpeg version git-2017-01-22-f1214ad Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --mandir=/usr/share/man --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libfreetype --enable-gnutls --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvidstab --enable-libwavpack --enable-nvenc
  libavutil      55. 44.100 / 55. 44.100
  libavcodec     57. 75.100 / 57. 75.100
  libavformat    57. 63.100 / 57. 63.100
  libavdevice    57.  2.100 / 57.  2.100
  libavfilter     6. 69.100 /  6. 69.100
  libavresample   3.  2.  0 /  3.  2.  0
  libswscale      4.  3.101 /  4.  3.101
  libswresample   2.  4.100 /  2.  4.100
  libpostproc    54.  2.100 / 54.  2.100 


  



  All I get is a blinking cursor and The stream.mp4 file is not written to disk after I exit (ctrl+c).

  



  So can you help me figure out :

  



  

  1. why wireshark cannot detect the packets as RTP (I suspect it has something to do with SDP)

  


  2. How to handle SDP answer when the RTP endpoint is pushing to ffmpeg which doesn't send an answer back.

  


  



  Here is the entire code (hello world tutorial modified)

  



  /*
     * (C) Copyright 2014-2015 Kurento (http://kurento.org/)
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *   http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    function getopts(args, opts)
    {
      var result = opts.default || {};
      args.replace(
          new RegExp("([^?=&]+)(=([^&]*))?", "g"),
          function($0, $1, $2, $3) { result[$1] = decodeURI($3); });

      return result;
    };

    var args = getopts(location.search,
    {
      default:
      {
        ws_uri: 'wss://' + location.hostname + ':8433/kurento',
        ice_servers: undefined
      }
    });

    function setIceCandidateCallbacks(webRtcPeer, webRtcEp, onerror)
    {
      webRtcPeer.on('icecandidate', function(candidate) {
        console.log("Local candidate:",candidate);

        candidate = kurentoClient.getComplexType('IceCandidate')(candidate);

        webRtcEp.addIceCandidate(candidate, onerror)
      });

      webRtcEp.on('OnIceCandidate', function(event) {
        var candidate = event.candidate;

        console.log("Remote candidate:",candidate);

        webRtcPeer.addIceCandidate(candidate, onerror);
      });
    }


    function setIceCandidateCallbacks2(webRtcPeer, rtpEp, onerror)
    {
      webRtcPeer.on('icecandidate', function(candidate) {
        console.log("Localr candidate:",candidate);

        candidate = kurentoClient.getComplexType('IceCandidate')(candidate);

        rtpEp.addIceCandidate(candidate, onerror)
      });
    }


    window.addEventListener('load', function()
    {
      console = new Console();

      var webRtcPeer;
      var pipeline;
      var webRtcEpt;

      var videoInput = document.getElementById('videoInput');
      var videoOutput = document.getElementById('videoOutput');

      var startButton = document.getElementById("start");
      var stopButton = document.getElementById("stop");

      startButton.addEventListener("click", function()
      {
        showSpinner(videoInput, videoOutput);

        var options = {
          localVideo: videoInput,
          remoteVideo: videoOutput
        };


        if (args.ice_servers) {
         console.log("Use ICE servers: " + args.ice_servers);
         options.configuration = {
           iceServers : JSON.parse(args.ice_servers)
         };
        } else {
         console.log("Use freeice")
        }

        webRtcPeer = kurentoUtils.WebRtcPeer.WebRtcPeerSendrecv(options, function(error)
        {
          if(error) return onError(error)

          this.generateOffer(onOffer)
        });

        function onOffer(error, sdpOffer)
        {
          if(error) return onError(error)

          kurentoClient(args.ws_uri, function(error, client)
          {
            if(error) return onError(error);

            client.create("MediaPipeline", function(error, _pipeline)
            {
              if(error) return onError(error);

              pipeline = _pipeline;

              pipeline.create("WebRtcEndpoint", function(error, webRtc){
                if(error) return onError(error);

                webRtcEpt = webRtc;

                setIceCandidateCallbacks(webRtcPeer, webRtc, onError)

                webRtc.processOffer(sdpOffer, function(error, sdpAnswer){
                  if(error) return onError(error);

                  webRtcPeer.processAnswer(sdpAnswer, onError);
                });
                webRtc.gatherCandidates(onError);

                webRtc.connect(webRtc, function(error){
                  if(error) return onError(error);

                  console.log("Loopback established");
                });
              });



            pipeline.create("RtpEndpoint", function(error, rtp){
                if(error) return onError(error);

                //setIceCandidateCallbacks2(webRtcPeer, rtp, onError)


                var cm_offer = "v=0\n" +
                      "o=- 3641290734 3641290734 IN IP4 127.0.0.1\n" +
                      "s=nginx\n" +
                      "c=IN IP4 127.0.0.1\n" +
                      "t=0 0\n" +
                      "m=audio 60820 RTP/AVP 0\n" +
                      "a=rtpmap:0 PCMU/8000\n" +
                      "a=recvonly\n" +
                      "m=video 59618 RTP/AVP 101\n" +
                      "a=rtpmap:101 H264/90000\n" +
                      "a=recvonly\n";



                rtp.processOffer(cm_offer, function(error, cm_sdpAnswer){
                  if(error) return onError(error);

                  //webRtcPeer.processAnswer(cm_sdpAnswer, onError);
                });
                //rtp.gatherCandidates(onError);

                webRtcEpt.connect(rtp, function(error){
                  if(error) return onError(error);

                  console.log("RTP endpoint connected to webRTC");
                });
              });









            });
          });
        }
      });
      stopButton.addEventListener("click", stop);


      function stop() {
        if (webRtcPeer) {
          webRtcPeer.dispose();
          webRtcPeer = null;
        }

        if(pipeline){
          pipeline.release();
          pipeline = null;
        }

        hideSpinner(videoInput, videoOutput);
      }

      function onError(error) {
        if(error)
        {
          console.error(error);
          stop();
        }
      }
    })


    function showSpinner() {
      for (var i = 0; i < arguments.length; i++) {
        arguments[i].poster = 'img/transparent-1px.png';
        arguments[i].style.background = "center transparent url('img/spinner.gif') no-repeat";
      }
    }

    function hideSpinner() {
      for (var i = 0; i < arguments.length; i++) {
        arguments[i].src = '';
        arguments[i].poster = 'img/webrtc.png';
        arguments[i].style.background = '';
      }
    }

    /**
     * Lightbox utility (to display media pipeline image in a modal dialog)
     */
    $(document).delegate('*[data-toggle="lightbox"]', 'click', function(event) {
      event.preventDefault();
      $(this).ekkoLightbox();
    });


  


• RTP packets detected as UDP

  28 février 2017, par user3172852

  Here is what I am trying to do :

  WebRTC endpoint > RTP Endpoint > ffmpeg > RTMP server.

  This is what my SDP file looks like.

  var cm_offer = "v=0\n" +
  
                "o=- 3641290734 3641290734 IN IP4 127.0.0.1\n" +
  
                "s=nginx\n" +
  
                "c=IN IP4 127.0.0.1\n" +
  
                "t=0 0\n" +
  
                "m=audio 60820 RTP/AVP 0\n" +
  
                "a=rtpmap:0 PCMU/8000\n" +
  
                "a=recvonly\n" +
  
                "m=video 59618 RTP/AVP 101\n" +
  
                "a=rtpmap:101 H264/90000\n" +
  
                "a=recvonly\n";

  What’s happening is that wireshark can detect the incoming packets at port 59618, but not as RTP packets but UDP packets. I am trying to capture the packets using ffmpeg with the following command :

  ubuntu@ip-132-31-40-100:~$ ffmpeg -i udp://127.0.0.1:59618 -vcodec copy stream.mp4
  
  ffmpeg version git-2017-01-22-f1214ad Copyright (c) 2000-2017 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  
    configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --mandir=/usr/share/man --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libfreetype --enable-gnutls --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvidstab --enable-libwavpack --enable-nvenc
  
    libavutil      55. 44.100 / 55. 44.100
  
    libavcodec     57. 75.100 / 57. 75.100
  
    libavformat    57. 63.100 / 57. 63.100
  
    libavdevice    57.  2.100 / 57.  2.100
  
    libavfilter     6. 69.100 /  6. 69.100
  
    libavresample   3.  2.  0 /  3.  2.  0
  
    libswscale      4.  3.101 /  4.  3.101
  
    libswresample   2.  4.100 /  2.  4.100
  
    libpostproc    54.  2.100 / 54.  2.100 

  All I get is a blinking cursor and The stream.mp4 file is not written to disk after I exit (ctrl+c).

  So can you help me figure out :

  1. why wireshark cannot detect the packets as RTP (I suspect it has something to do with SDP)
  2. How to handle SDP answer when the RTP endpoint is pushing to ffmpeg which doesn’t send an answer back.

  Here is the entire code (hello world tutorial modified)

  /*
  
       * (C) Copyright 2014-2015 Kurento (http://kurento.org/)
  
       *
  
       * Licensed under the Apache License, Version 2.0 (the "License");
  
       * you may not use this file except in compliance with the License.
  
       * You may obtain a copy of the License at
  
       *
  
       *   http://www.apache.org/licenses/LICENSE-2.0
  
       *
  
       * Unless required by applicable law or agreed to in writing, software
  
       * distributed under the License is distributed on an "AS IS" BASIS,
  
       * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  
       * See the License for the specific language governing permissions and
  
       * limitations under the License.
  
       */
  
  
  
      function getopts(args, opts)
  
      {
  
        var result = opts.default || {};
  
        args.replace(
  
            new RegExp("([^?=&]+)(=([^&]*))?", "g"),
  
            function($0, $1, $2, $3) { result[$1] = decodeURI($3); });
  
  
  
        return result;
  
      };
  
  
  
      var args = getopts(location.search,
  
      {
  
        default:
  
        {
  
          ws_uri: 'wss://' + location.hostname + ':8433/kurento',
  
          ice_servers: undefined
  
        }
  
      });
  
  
  
      function setIceCandidateCallbacks(webRtcPeer, webRtcEp, onerror)
  
      {
  
        webRtcPeer.on('icecandidate', function(candidate) {
  
          console.log("Local candidate:",candidate);
  
  
  
          candidate = kurentoClient.getComplexType('IceCandidate')(candidate);
  
  
  
          webRtcEp.addIceCandidate(candidate, onerror)
  
        });
  
  
  
        webRtcEp.on('OnIceCandidate', function(event) {
  
          var candidate = event.candidate;
  
  
  
          console.log("Remote candidate:",candidate);
  
  
  
          webRtcPeer.addIceCandidate(candidate, onerror);
  
        });
  
      }
  
  
  
  
  
      function setIceCandidateCallbacks2(webRtcPeer, rtpEp, onerror)
  
      {
  
        webRtcPeer.on('icecandidate', function(candidate) {
  
          console.log("Localr candidate:",candidate);
  
  
  
          candidate = kurentoClient.getComplexType('IceCandidate')(candidate);
  
  
  
          rtpEp.addIceCandidate(candidate, onerror)
  
        });
  
      }
  
  
  
  
  
      window.addEventListener('load', function()
  
      {
  
        console = new Console();
  
  
  
        var webRtcPeer;
  
        var pipeline;
  
        var webRtcEpt;
  
  
  
        var videoInput = document.getElementById('videoInput');
  
        var videoOutput = document.getElementById('videoOutput');
  
  
  
        var startButton = document.getElementById("start");
  
        var stopButton = document.getElementById("stop");
  
  
  
        startButton.addEventListener("click", function()
  
        {
  
          showSpinner(videoInput, videoOutput);
  
  
  
          var options = {
  
            localVideo: videoInput,
  
            remoteVideo: videoOutput
  
          };
  
  
  
  
  
          if (args.ice_servers) {
  
           console.log("Use ICE servers: " + args.ice_servers);
  
           options.configuration = {
  
             iceServers : JSON.parse(args.ice_servers)
  
           };
  
          } else {
  
           console.log("Use freeice")
  
          }
  
  
  
          webRtcPeer = kurentoUtils.WebRtcPeer.WebRtcPeerSendrecv(options, function(error)
  
          {
  
            if(error) return onError(error)
  
  
  
            this.generateOffer(onOffer)
  
          });
  
  
  
          function onOffer(error, sdpOffer)
  
          {
  
            if(error) return onError(error)
  
  
  
            kurentoClient(args.ws_uri, function(error, client)
  
            {
  
              if(error) return onError(error);
  
  
  
              client.create("MediaPipeline", function(error, _pipeline)
  
              {
  
                if(error) return onError(error);
  
  
  
                pipeline = _pipeline;
  
  
  
                pipeline.create("WebRtcEndpoint", function(error, webRtc){
  
                  if(error) return onError(error);
  
  
  
                  webRtcEpt = webRtc;
  
  
  
                  setIceCandidateCallbacks(webRtcPeer, webRtc, onError)
  
  
  
                  webRtc.processOffer(sdpOffer, function(error, sdpAnswer){
  
                    if(error) return onError(error);
  
  
  
                    webRtcPeer.processAnswer(sdpAnswer, onError);
  
                  });
  
                  webRtc.gatherCandidates(onError);
  
  
  
                  webRtc.connect(webRtc, function(error){
  
                    if(error) return onError(error);
  
  
  
                    console.log("Loopback established");
  
                  });
  
                });
  
  
  
  
  
  
  
              pipeline.create("RtpEndpoint", function(error, rtp){
  
                  if(error) return onError(error);
  
  
  
                  //setIceCandidateCallbacks2(webRtcPeer, rtp, onError)
  
  
  
  
  
                  var cm_offer = "v=0\n" +
  
                        "o=- 3641290734 3641290734 IN IP4 127.0.0.1\n" +
  
                        "s=nginx\n" +
  
                        "c=IN IP4 127.0.0.1\n" +
  
                        "t=0 0\n" +
  
                        "m=audio 60820 RTP/AVP 0\n" +
  
                        "a=rtpmap:0 PCMU/8000\n" +
  
                        "a=recvonly\n" +
  
                        "m=video 59618 RTP/AVP 101\n" +
  
                        "a=rtpmap:101 H264/90000\n" +
  
                        "a=recvonly\n";
  
  
  
  
  
  
  
                  rtp.processOffer(cm_offer, function(error, cm_sdpAnswer){
  
                    if(error) return onError(error);
  
  
  
                    //webRtcPeer.processAnswer(cm_sdpAnswer, onError);
  
                  });
  
                  //rtp.gatherCandidates(onError);
  
  
  
                  webRtcEpt.connect(rtp, function(error){
  
                    if(error) return onError(error);
  
  
  
                    console.log("RTP endpoint connected to webRTC");
  
                  });
  
                });
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
              });
  
            });
  
          }
  
        });
  
        stopButton.addEventListener("click", stop);
  
  
  
  
  
        function stop() {
  
          if (webRtcPeer) {
  
            webRtcPeer.dispose();
  
            webRtcPeer = null;
  
          }
  
  
  
          if(pipeline){
  
            pipeline.release();
  
            pipeline = null;
  
          }
  
  
  
          hideSpinner(videoInput, videoOutput);
  
        }
  
  
  
        function onError(error) {
  
          if(error)
  
          {
  
            console.error(error);
  
            stop();
  
          }
  
        }
  
      })
  
  
  
  
  
      function showSpinner() {
  
        for (var i = 0; i < arguments.length; i++) {
  
          arguments[i].poster = 'img/transparent-1px.png';
  
          arguments[i].style.background = "center transparent url('img/spinner.gif') no-repeat";
  
        }
  
      }
  
  
  
      function hideSpinner() {
  
        for (var i = 0; i < arguments.length; i++) {
  
          arguments[i].src = '';
  
          arguments[i].poster = 'img/webrtc.png';
  
          arguments[i].style.background = '';
  
        }
  
      }
  
  
  
      /**
  
       * Lightbox utility (to display media pipeline image in a modal dialog)
  
       */
  
      $(document).delegate('*[data-toggle="lightbox"]', 'click', function(event) {
  
        event.preventDefault();
  
        $(this).ekkoLightbox();
  
      });

• Hacking the Popcorn Hour C-200

  3 mai 2010, par Mans — Hardware, MIPS

  Update : A new firmware version has been released since the publication of this article. I do not know if the procedure described below will work with the new version.

  The Popcorn Hour C-200 is a Linux-based media player with impressive specifications. At its heart is a Sigma Designs SMP8643 system on chip with a 667MHz MIPS 74Kf as main CPU, several co-processors, and 512MB of DRAM attached. Gigabit Ethernet, SATA, and USB provide connectivity with the world around it. With a modest $299 on the price tag, the temptation to repurpose the unit as a low-power server or cheap development board is hard to resist. This article shows how such a conversion can be achieved.
  

  Kernel

  The PCH runs a patched Linux 2.6.22.19 kernel. A source tarball is available from the manufacturer. This contains the sources with Sigma support patches, Con Kolivas’ patch set (scheduler tweaks), and assorted unrelated changes. Properly split patches are unfortunately not available. I have created a reduced patch against vanilla 2.6.22.19 with only Sigma-specific changes, available here.

  The installed kernel has a number of features disabled, notably PTY support and oprofile. We will use kexec to load a more friendly one.

  As might be expected, the PCH kernel does not have kexec support enabled. It does however, by virtue of using closed-source components, support module loading. This lets us turn kexec into a module and load it. A patch for this is available here. To build the module, apply the patch to the PCH sources and build using this configuration. This will produce two modules, kexec.ko and mips_kexec.ko. No other products of this build will be needed.

  The replacement kernel can be built from the PCH sources or, if one prefers, from vanilla 2.6.22.19 with the Sigma-only patch. For the latter case, this config provides a minimal starting point suitable for NFS-root.

  When configuring the kernel, make sure CONFIG_TANGOX_IGNORE_CMDLINE is enabled. Otherwise the command line will be overridden by a useless one stored in flash. A good command line can be set with CONFIG_CMDLINE (under “Kernel hacking” in menuconfig) or passed from kexec.

  Taking control

  In order to load our kexec module, we must first gain root privileges on the PCH, and here a few features of the system are working to our advantage :

  1. The PCH allows mounting any NFS export to access media files stored there.
  2. There is an HTTP server running. As root.
  3. This HTTP server can be readily instructed to fetch files from an NFS mount.
  4. Files with a name ending in .cgi are executed. As root.

  All we need do to profit from this is place the kexec modules, the kexec userspace tools, and a simple script on an NFS export. Once this is done, and the mount point configured on the PCH, a simple HTTP request will send the old kernel screaming to /dev/null, our shiny new kernel taking its place.

  The rootfs

  A kernel is mostly useless without a root filesystem containing tools and applications. A number of tools for cross-compiling a full system exist, each with its strengths and weaknesses. The only thing to look out for is the version of kernel headers used (usually a linux-headers package). As we will be running an old kernel, chances are the default version is too recent. Other than this, everything should be by the book.

  Assembling the parts

  Having gathered all the pieces, it is now time to assemble the hack. The following steps are suitable for an NFS-root system. Adaptation to a disk-based system is left as an exercise.

  1. Build a rootfs for MIPS 74Kf little endian. Make sure kernel headers used are no more recent than 2.6.22.x. Include a recent version of the kexec userspace tools.
  2. Fetch and unpack the PCH kernel sources.
  3. Apply the modular kexec patch.
  4. Using this config, build the modules and install them as usual to the rootfs. The version string must be 2.6.22.19-19-4.
  5. From either the same kernel sources or plain 2.6.22.19 with Sigma patches, build a vmlinux and (optionally) modules using this config. Modify the compiled-in command line to point to the correct rootfs. Set the version string to something other than in the previous step.
  6. Copy vmlinux to any directory in the rootfs.
  7. Copy kexec.sh and kexec.cgi to the same directory as vmlinux.
  8. Export the rootfs over NFS with full read/write permissions for the PCH.
  9. Power on the PCH, and update to latest firmware.
  10. Configure an NFS mount of the rootfs.
  11. Navigate to the rootfs in the PCH UI. A directory listing of bin, dev, etc. should be displayed.
  12. On the host system, run the kexec.sh script with the target hostname or IP address as argument.
  13. If all goes well, the new kernel will boot and mount the rootfs.

  Serial console

  A serial console is indispensable for solving boot problems. The PCH board has two UART connectors. We will use the one labeled UART0. The pinout is as follows (not standard PC pinout).

          +-----------+
         2| * * * * * |10
         1| * * * * * |9
          -----------+
            J7 UART0
      /---------------------/ board edge
  

  Pin	Function
  1	+5V
  5	Rx
  6	Tx
  10	GND

  The signals are 3.3V so a converter, e.g. MAX202, is required for connecting this to a PC serial port. The default port settings are 115200 bps 8n1.