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• How can I quantitatively measure gstreamer H264 latency between source and display ?

  16 décembre 2014, par KevinM

  I have a project where we are using gstreamer , x264, etc, to multicast a video stream over a local network to multiple receivers (dedicated computers attached to monitors). We’re using gstreamer on both the video source (camera) systems and the display monitors.

  We’re using RTP, payload 96, and libx264 to encode the video stream (no audio).

  But now I need to quantify the latency between (as close as possible to) frame acquisition and display.

  Does anyone have suggestions that use the existing software ?

  Ideally I’d like to be able to run the testing software for a few hours to generate enough statistics to quantify the system. Meaning that I can’t do one-off tests like point the source camera at the receiving display monitor displaying a high resolution and manually calculate the difference...

  I do realise that using a pure software-only solution, I will not be able to quantify the video acquisition delay (i.e. CCD to framebuffer).

  I can arrange that the system clocks on the source and display systems are synchronised to a high accuracy (using PTP), so I will be able to trust the system clocks (else I will use some software to track the difference between the system clocks and remove this from the test results).

  In case it helps, the project applications are written in C++, so I can use C event callbacks, if they’re available, to consider embedding system time in a custom header (e.g. frame xyz, encoded at time TTT - and use the same information on the receiver to calculate a difference).

• FFMPEG + SDL : How To Show Multi Frames In Separate Region ?

  19 mai 2014, par user3051473

  I’m using ffmpeg and SDL to develop an camera monitor APP and I want to show four separate streams at the same time(via four rtsp source). As following figure out :

  Now I achieve this by setting the SDL display region, and I identify different display region by using the different SDL_Rect identifying by the variable i(from 1 - 4).

  But this cause the efficient problem. For every region, I need to scale to the whole screen and lock/unlock screen, then display.

  I’m wondering that, Can I merge 4 different AVFrame(come from REG1 - REG4) into the whole picture and then show this picture ?

  Hope that the describe about is detail enough for you to konw my problem.
  Also thanks for your help.

  -------------------
  
  -        -        -
  
  -  REG1  -  REG2  -
  
  -        -        -
  
  -------------------
  
  -        -        -
  
  -  REG3  -  REG4  -
  
  -        -        -
  
  -------------------
  
  
  
  public void ShowFrame(AVFrame *pFrame, AVCodecContext *pCodecContext)
  
  {
  
      SDL_LockYUVOverlay(pBmp);
  
      AVPicture pict;
  
  
  
      // TODO scale pFrame to pict
  
      // ...
  
  
  
      SDL_UnlockYUVOverlay(pBmp);
  
  
  
      // WIDTH and HEIGHT represent the whole screen size
  
      SDL_Rect rect;
  
      rect.x = (WIDTH / 2) * (i % 2);
  
      rect.y = (HEIGHT / 2) * (i > 1 ? 1: 0);
  
      rect.w = WIDTH / 2;
  
      rect.h = HEIGHT / 2;
  
      SDL_DisplayYUVOverlay(pBmp, &rect);
  
  }

• Capture video with audio by ffmpeg and pass it to hdmi out

  22 octobre 2020, par Rougher

  I need to pass through video/data from my laptop to TV Monitor through linux computer (Raspberry Pi, for example) while capturing passed data in rpi.

  


  my laptop ---> video capture card ---> linux computer (save to external storage) ----> TV monitor

  


  How can I do this ?

  


  Maybe I can do it with ffmpeg ? But I don't understand how to transmit output to hdmi instead of a file.