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• How to install codecs for opencv ?

  4 mars 2015, par user2565010

  I am trying to write a program that captures video from a webcam using this code :

  #include <opencv2></opencv2>core/core.hpp>
  
  #include <opencv2></opencv2>highgui/highgui.hpp>
  
  #include <iostream>
  
  
  
  using namespace cv;
  
  using namespace std;
  
  
  
  int main(int argc, char** argv)
  
  {
  
  
  
      Mat frame;
  
      VideoCapture cap(1);
  
      char key;
  
      String outputName = "output.avi";
  
  
  
      VideoWriter outputVideo;
  
      Size size = Size(cap.get(CV_CAP_PROP_FRAME_WIDTH), cap.get(CV_CAP_PROP_FRAME_HEIGHT));
  
  
  
  
  
  
  
      outputVideo.open(outputName, CV_FOURCC('D', 'I', 'V', 'X'), cap.get(CV_CAP_PROP_FPS), size, true);
  
  
  
      if (!outputVideo.isOpened())
  
      {
  
          cout &lt;&lt; "Could not open the output video for write: " &lt;&lt; outputName &lt;&lt; endl;
  
          return -1;
  
      }
  
      cout &lt;&lt; "size " &lt;&lt; size.width &lt;&lt; " x " &lt;&lt; size.height &lt;&lt; endl;
  
  
  
      namedWindow("Display window", WINDOW_AUTOSIZE); // Create a window for display.
  
      cap.set(CV_CAP_PROP_EXPOSURE, -8);
  
  
  
  
  
      while (true){
  
          bool success = cap.read(frame);
  
          if (!success){
  
              cout &lt;&lt; "Cannot read frame from file" &lt;&lt; endl;
  
              return -2;
  
          }
  
          outputVideo.write(frame);
  
          imshow("Display window", frame);
  
          key = waitKey(1);
  
          if (key == ' '){
  
              cout &lt;&lt; "Video ended due to key stroke" &lt;&lt; endl;
  
              return 1;
  
          }
  
      }
  
  
  
  
  
      return 0;
  
  }
  
  </iostream>

  The program doesn’t seem to be able to open outputVideo since it always returns -1. I thought that I might not have the codec divx installed, but I have installed it from k-lite codec pack and divx and it still does not work.

  Could anybody please tell me how to install codecs such that opencv recognizes them ?

  I am using OpenCV 2.4.10 on Windows 7 with Visual studio 2013.

• Are there people interested in converting ffmpeg source to Go ?

  30 septembre 2018, par No One

  After seeing that Go compiler have been converted from C to Go I thought same for ffmpeg ? Don’t want to go deep into reasons as I think they are obvious. It was very hard to be so close to the have rich library as ffmpeg in other language. It was even hard to make bindings for that scale of library. I’m not enough advanced to start something like this myself, so is there anybody else interested in this ? If yes then where this question worth to be addressed, so people interested in this may have discussion ?

  (Seems not enough obvious so adding some details.)

  For applications which use large amount of commands with different complexity it is hard to read the code as it’s not actually a code. Instead, it’s commands which you will need to understand by reading docs from ffmpeg’s docs page. I had used ffmpeg before in Nodejs and there was lots of logic of manipulating command string. Also sometimes in windows it was ending with cmd limitations error. When you are working with some language it is nice to see whole logic in that language. So you know go ? than you know everything that is happening with this code without even going off from code and reading docs of another application.

  There may be some benefits from executing stuff in goroutines so you can handle concurrency in the way you want not in the way it is implemented in ffmpeg.

  Build faster with Go.

  Less code.

  Possibility to split code into smaller packages.

  Also if you are familiar why community converted compiler from C to Go than I think some reasons will fit too.

• swscale/x86/output : add AVX2 version of yuv2nv12cX

  26 avril 2020, par Nelson Gomez

  swscale/x86/output : add AVX2 version of yuv2nv12cX
  256 bits is just wide enough to fit all the operands needed to vectorize
  
  the software implementation, but AVX2 is needed to for a couple of
  
  instructions like cross-lane permutation.
  Output is bit-for-bit identical to C.
  Signed-off-by : Nelson Gomez <nelson.gomez@microsoft.com>
  

  • [DH] libswscale/x86/output.asm
  • [DH] libswscale/x86/swscale.c