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• OpenCV 4.5.2 VideoWriter produces “can't find starting number” error

  28 avril 2021, par Peter Kronenberg

  There are several issues with similar names, but none of them seem to have a definitive answer. Using the last version of OpenCV 4.5.2 with Java on Windows 10. Below is a short reproducible test case which results in

  


  [ERROR:0] global C:\build\master_winpack-bindings-win64-vc14-static\opencv\modules\videoio\src\cap.cpp (589) cv::VideoWriter::open VIDEOIO(CV_IMAGES): raised OpenCV exception:

OpenCV(4.5.2) C:\build\master_winpack-bindings-win64-vc14-static\opencv\modules\videoio\src\cap_images.cpp:253: error: (-5:Bad argument) CAP_IMAGES: can't find starting number (in the name of file): C:/testfiles/output.avi in function 'cv::icvExtractPattern'


  


  Here is the code :

  


  public class OpenCVError {

    public static void main(String[] args) {
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);

        final int fourcc = VideoWriter.fourcc('m', 'j', 'p', 'g');
        final double fps = 30.00;
        Size frameSize = new Size(1080, 1920);
        VideoWriter videoWriter = new VideoWriter("C:/testfiles/output.avi", fourcc, fps, frameSize, true);
    }
}


  


  Update

  


  Found out from https://forum.opencv.org/t/error-in-java-cant-find-starting-number-in-the-name-of-file/3014 that I seem to be missing opencv_videoio_ffmpeg452_64.dll
I am using the Maven distribution at

  


    <dependency>&#xA;            <groupid>org.openpnp</groupid>&#xA;            <artifactid>opencv</artifactid>&#xA;            <version>4.5.1-2</version>&#xA;  </dependency>&#xA;

  


  which doesn't appear to have this file. I tried adding the file to my classpath (using IntelliJ), but it still doesn't seem to work.

  


  Anyone have any ideas ? Why isn't this file part of the openpnp distribution ?

  


• Streaming Video from RTMP to EMGUCV

  22 juillet 2017, par Isuru

  I’m trying to stream a webcam using RTMP to an EMGUCV project in order to process the video. I have set up a private RTMP server in a linux box using this tutorial,
  https://obsproject.com/forum/resources/how-to-set-up-your-own-private-rtmp-server-using-nginx.50/

  I’m testing the webcam stream using ffmpeg with the following commands,

  • Write to the rtmp server using,

    ffmpeg -y -f vfwcap -framerate 25 -video_size 640x480 -i 0 -an -f flv rtmp://rtmp-server:1935/live/stream

  • Read from the rtmp server using,
    ffplay -fflags nobuffer rtmp ://rtmp-server:1935/live/stream -loglevel verbose

  I’m able to write a simple OpenCV C++ application to read the stream and display it. Code below,

      cv::VideoCapture vcap;
  
      cv::Mat image;
  
      const std::string videoStreamAddress = "rtmp://rtmp-server:1935/live/stream";
  
      if(!vcap.open(videoStreamAddress)) {
  
          printf("Error opening video stream or file");
  
          return -1;
  
      }
  
  
  
      cv::namedWindow("Output Window");
  
      cv::Mat edges;
  
      for(;;) {
  
          if(!vcap.read(image)) {
  
              printf("No frame");
  
              cv::waitKey();
  
          }
  
          cv::imshow("Output Window", image);
  
          if(cv::waitKey(1) >= 0) break;
  
      }
  
  return 0;

  The above code works properly. However when I try it using EMGUCV C#, I get the error message
  unable to create to capture from rtmp://rtmp-server:1935/live/stream

  This is my C# Code,

      public partial class MainForm : Form
  
      {
  
          private static Capture _cameraCapture;
  
  
  
          public MainForm()
  
          {
  
              InitializeComponent();
  
              Run();
  
          }
  
  
  
          void Run()
  
          {
  
              try
  
              {
  
                  _cameraCapture = new Capture("rtmp://192.168.56.101:1935/live/stream");                
  
              }
  
              catch (Exception e)
  
              {
  
                  MessageBox.Show(e.Message);
  
                  return;
  
              }            
  
          }
  
     }

  Do I need a specific build of EMGUCV with FFMPEG or is RTMP capturing not available in EMGUCV ?

• Evolution #2173 (Résolu) : Date de création / publication

  13 janvier 2018, par nico d_

  J’ai ajouté la doc du plugin : https://contrib.spip.net/ecrire/?exec=article&id_article=4967

  Pas encore publiée, mais je propose de fermer ce ticket dès qu’elle le sera, et de continuer la discussion sur le forum du plugin sur contrib.