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• Révision 17269 : attention : statut est un tableau dont chaque element est un tableau decrivant l...

  18 février 2011, par cedric -

  + utiliser la description venant de $boucle->show lors de la compilation

• EmguCV capture rtsp ip camera stream ffmpeg

  2 février 2018, par Mr Neo

  I am working with IP camera and EmguCV to detect person in an area.
  Everything is work normally with Highgui capture source.
  But with Arlo camera which use FFMPEG format, I am unable to get stream without any exception.
  Here is the code I have tried :

  if (capture == null)
  
          {
  
              try
  
              {
  
                  capture = new Capture("rtsp://<ip>:8554/live"); 
  
                  capture.ImageGrabbed += Capture_ImageGrabbed;
  
                  capture.Grab();
  
                  capture.Start();
  
              }
  
  
  
  
  
              catch (NullReferenceException exception)
  
              {
  
                  MessageBox.Show(exception.Message);
  
              }
  
              catch (TypeInitializationException exc)
  
              {
  
                  MessageBox.Show(
  
                     "Attention: You have to copy all the assemblies and native libraries from an official release of EmguCV to the directory of the demo." +
  
                     Environment.NewLine + Environment.NewLine + exc);
  
              }
  
  }
  
  </ip>

  and here is Capture_ImageGrabbed event which is not fired.

  private void Capture_ImageGrabbed(object sender, EventArgs e)
  
      {
  
          Mat image = new Mat();
  
          capture.Retrieve(image);
  
          picCAM.Image = image.Bitmap;
  
      }

  Thanks so much for your help !

• ffmpeg outputs that the first frame of a 25fps video shows for only 1ms

  13 avril 2019, par Chubacca

  I’m using ffmpeg to split up a video by frames. For a video that is 25fps, my expectation would be that it would show frame 0 for 40ms, and then it would show frame 1 for 40ms, etc. However, when I use ffmepg to analyze the video, this is not what I get.

  I pulled frames out of the video using the following commands :

  ffmpeg -i original.mp4 -ss 00:00:00.000 -vframes 1 0.000.png
  
  ffmpeg -i original.mp4 -ss 00:00:00.001 -vframes 1 0.001.png
  
  ffmpeg -i original.mp4 -ss 00:00:00.040 -vframes 1 0.040.png
  
  ffmpeg -i original.mp4 -ss 00:00:00.041 -vframes 1 0.041.png

  In this, I would expect 0.000.png and 0.001.png to be the same frame, but the resulting pngs are different. However, on the flipside, 0.001.png and 0.040.png ARE the same frame, while 0.040.png and 0.041.png are different frames. It seems as though the frame at 0.000.png is only showing for 1ms. I’ve tested this on multiple different videos, with consistent results. Can anybody explain why this is or why my expectations are potentially incorrect ?

  As a side note, when I load the same video into an HTML5 video tag in the browsers, when I play the video the first frame shows for 64 milliseconds, and all other frames show for 40 milliseconds. I can test this by comparing frames for the following commands :

  player.currentTime = 0
  
  player.currentTime = .063 // same frame as 0
  
  player.currentTime = .064 // different frame than .063
  
  player.currentTime = .103 // same frame as .064
  
  player.currentTime = .104 // different frame than .103

  This also defies expectations, and makes matching up frames/times for the video between ffmpeg and html5 video even more annoying. Does anyone know what’s going on here ?

  If it’s helpful, here is the metadata from the video :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'original.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf58.17.101
  
    Duration: 01:36:16.20, start: 0.000000, bitrate: 2301 kb/s
  
      Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 2200 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 96 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler