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• Make video frames from a livestream identifiable across multiple clients

  23 septembre 2016, par mschwaig

  I need to distribute a video stream from a live source to several clients with the additional requirement that each frame is identifiable across all clients.

  I have already done research into the topic, and I have arrived at a possible solution that I can share. My solution seems suboptimal and this is my first experience of working with video streams, so I want to see if somebody knows a better way.

  The reason why I need to be able to identify specific frames within the video stream is that the streaming clients need to be able to talk about the time differences between events each of them identifies in their video stream.

  A little clarifying example

  I want to enable the following interaction :

  • Two client applications Dewey and Stevie connect to the streaming server
  • Dewey displays the stream and Stevie saves it to disk
  • Dewey identifies a specific video frame that is of interest to Stevie, so he wants to tell Stevie about it
  • Dewey extracts some identifying information from the video frame and sends it to Stevie
  • Stevie uses the identifying information to extract the same frame from the copy of the livestream he is currently saving

  Dewey cannot send the frame to Stevie directly, because Malcolm and Reese also want to tell him about specific video frames and Stevie is interested in the time difference between their findings.

  Suggested solution

  The solution that I found was using ffserver to broadcast a RTP stream and use the timestamps from the RTCP packets to identify frames. These timestamps are normally used to synchronize audio and video, and not to provide a shared timeline across several clients, which is why I am skeptical this is the best way to solve my problem.

  It also seems beneficial to have frame numbers, like an increasing counter of frames instead of arbitrary timestamps which increase by some perhaps varying offset as for my application I also have to reference neighboring frames and it seems easier to compute time differences from frame numbers, than the other way around.

• ffmpeg/h265/opencv/c++ A method to resize frame after decoding on client side

  18 janvier 2018, par 8793

  I’ve just joined a project to build a realtime video streaming application using ffmpeg/opencv/c++ via udp socket. On server side, they want to transmit a video size (640x480) to client, in order to reduce data transmission through network I resize the video to (320x240) and send frame. On client side (client), after receiving frame, we will upscale the frame back to (640x480). Using H265 for encode/decoding.

  As I am just a beginner with video encoding, I would like to understand how to down-sampling & up-sampling the frame at server & client side in which we can incorporate with the video encoder/decoder.

  A simple idea came into my mind that after decoding avframe -> Mat frame, I will upsampling this frame then display it.

  I am not sure my idea is right or wrong. I would like to seek advice from any people who had experience in this area. Thank you very much !

  static void updateFrameCallback(AVFrame *avframe, void* userdata) {
  
      VideoStreamUDPClient* streamer = static_cast (userdata);
  
      TinyClient* client = static_cast (streamer->userdata);
  
  
  
      //Update Frame
  
      pthread_mutex_lock(&client->mtx_updateFrame);
  
      if (streamer->irect.width == client->frameSize.width
  
              && streamer->irect.height == client->frameSize.height) {
  
          cvtAVFrameYUV4202Frame(&avframe, client->frame);
  
          printf("TinyClient: Received Full Frame\n");
  
      } else {
  
          Mat block;
  
          cvtAVFrameYUV4202Frame(&avframe, block);
  
          block.copyTo(client->frame(streamer->irect));
  
      }
  
  
  
      //How to resize frame before display it!!!
  
  
  
      imshow("Frame", client->frame);
  
      waitKey(1);
  
      pthread_mutex_unlock(&client->mtx_updateFrame);
  
  }

• FFMPEG with SSM is not using the specified network interface

  23 janvier 2014, par caspar

  I'm trying to use ffmpeg/ffprobe to join a SSM stream on a server with multiple network interfaces. I'm using the following command to initialize the input :

  c:\ffmpeg\bin>ffprobe "udp://232.2.4.206:24206?localaddr=10.15.248.217&sources=10.15.248.210,10.15.248.211,10.15.248.212,10.15.248.213&connect=1&fifo_size=1000000" -v 9 -loglevel 99

  The routing on the server can't be changed, though I can confirm other applications running on the same server are able to join and receive the multicast signal. The issue is, I believe, with the localaddr parameter, which is ignored it seems. Using Wireshark I can see that the wrong interface is being used (i.e. not the 10.15.248.217 interface).

  The output of the above command is :

  ffprobe version N-60087-g94a5241 Copyright (c) 2007-2014 the FFmpeg developers
  
  built on Jan 21 2014 22:06:13 with gcc 4.8.2 (GCC)
  
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetype --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
  
  libavutil      52. 63.100 / 52. 63.100
  
  libavcodec     55. 48.102 / 55. 48.102
  
  libavformat    55. 25.101 / 55. 25.101
  
  libavdevice    55.  5.102 / 55.  5.102
  
  libavfilter     4.  1.100 /  4.  1.100
  
  libswscale      2.  5.101 /  2.  5.101
  
  libswresample   0. 17.104 /  0. 17.104
  
  libpostproc    52.  3.100 / 52.  3.100
  
  [udp @ 000000000272dcc0] end receive buffer size reported is 65536

  Anyone have experience with this use case ? Perhaps this is a bug that needs raising ?

  EDIT : I found out that if I remove the &sources= parameter, the localaddr is used and the request is passed through the correct interface, however as I need to join a SSM stream, this still blocks me from continuing.