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• How To Extract RTP Packet Specific Fields From Wireshark Capture ?

  5 novembre 2014, par Lane

  I have a PCAPNG file and I need to get the RTP packets from it. Specifically, one of my RTP packets looks like...

  Frame N : X bytes on wire...

  • Ethernet II, Src : ...
  • IPv4, Src : ...
  • TCP, Src Port : rstp ...
  • RTSP Interleaved Frame, Channel : 0x02, 163 bytes
  • Real-Time Transport Protocol

  ...and what I need from each packet is...

  1. The channel from the RTSP interleaved frame
  2. The length from the RTSP interleaved frame
  3. The payload from the RTP

  ...using this data, I will re-create an audio and video file to re-construct the full video from a local payload (playback is not streaming).

  I am able to successfully get the RTP packets using either...

  tshark -r my.pcap -R -T fields -e rtp.payload -w rtp.out

  or...

  tshark -r my.pcap -R -T fields -e rtp.payload > rtp.out

  ...but the problem I am having is that the first method will save everything I need, but for some reason it will add extra data (i.e. more than just the RTP payload and RTSP interleaved frame contents) in strange places... which is preventing me from writing a program to produce the data I need to test. I attempted to remove all the extra data using several regular expressions, but there are too many different scenarios that overlap onto other valid scenarios.

  The second method will provide only the RTP payload without the interleaved properties I need (it will produce the hex with a colon between each byte, but that is easily handled). Even if I could make another call to get all the RTSP interleaved frame properties, I am going to need to combine the 2 outputs by identifying each packet using a separator / delimiter, which I’d like to avoid (I couldn’t get tshark to do that either...).

  I looked into the tshark read filters, which seems like it should be able to do what I need, but so far I haven’t been able to figure it out. Note that I am only doing this to create sample data and write the logic that formats the data required for playback. Eventually one of my co-workers will modify the streaming client to capture the data in the appropriate format (so I can simply run the data through ffmpeg without modifying it). Any ideas of how I can create the format I need ?

• lavc/codec_desc : add a property for codecs that support field coding

  5 mai 2023, par Anton Khirnov

  lavc/codec_desc : add a property for codecs that support field coding
  Multiple places currently use AVCodecContext.ticks_per_frame > 1 to
  
  identify such codecs, which
  
  * requires a codec context
  
  * requires it to be open
  

  • [DH] doc/APIchanges
  • [DH] libavcodec/codec_desc.c
  • [DH] libavcodec/codec_desc.h
  • [DH] libavcodec/version.h

• Using ffmpeg to convert audio from Red5

  19 août 2014, par Chintan Patel

  I am facing some problems in my project.

  In my project, I need to implement microphone integration with RED5 server using Actionscript which is used to store the audio stream on server and after that I used ffmpeg in java code to convert the flv file to mp3.

  I am facing 2 problems here :

  1. The recorded audio creates .flv file which is currepted.

  2. When I try to convert the .flv to .mp3 using ffmpeg, it gets stuck until I stop the Red5 server.

  Here is my code of both places. Please let me know where I am doing wrong.

  Actionscipt to record microphone audio and stream on red5 :

  private function initConnection():Void {
  
  
  
          trace("Connecting...");
  
  
  
          nc = new NetConnection();
  
          nc.client = this;
  
          nc.addEventListener(NetStatusEvent.NET_STATUS, onNetConnectionStatus);
  
          nc.connect("rtmp://127.0.0.1/test");
  
  
  
          this.mic = Microphone.getMicrophone();
  
  
  
          if (this.mic != null) {
  
              this.mic.rate = 44;
  
              mic.setSilenceLevel(0);
  
              mic.gain = 100;
  
              mic.setUseEchoSuppression(true); 
  
              mic.setLoopBack(true);              
  
          }                   
  
      }

  To Send on Red5 :

  public function startSending( nc: NetConnection, filename:String ) {
  
          ns = new NetStream(nc);
  
          ns.addEventListener(NetStatusEvent.NET_STATUS, onNetStreamStatus);
  
          ns.publish(filename, 'record');
  
          ns.attachAudio(mic);        
  
  }

  To Stop recording/sending :

  public function stopSending() {
  
          mic.setLoopBack(false);
  
          ns.attachAudio(null);
  
          ns.close();     
  
  }

  The resulting .flv stored on server which is currepted.

  Not to convert .flv into .mp3, I have used ffmpeg in my Java code as per following :

  String ffmpegArgs[] = {executableDir,"-i",flvFile.getAbsolutePath(), "-vn", mp3File.getAbsolutePath()};
  
  Process process = new ProcessBuilder(Arrays.asList(ffmpegArgs)).start();

  This starts the file conversion, but it gets stucked. After some time when I stop the server, it immediately shows the converted file.
  Please let me know, where I am doing wrong.