Recherche avancée

Sur d’autres sites (6173)

• OpenCV : in search for less CPU intensive frame capture+resize and into buffer way : how to optimize my code ?

  18 septembre 2014, par Rella

  So I created a function (C++)

  void CaptureFrame(char* buffer, int w, int h, int bytespan)
  
  {
  
   /* get a frame */
  
   if(!cvGrabFrame(capture)){              // capture a frame 
  
    printf("Could not grab a frame\n\7");
  
    //exit(0);
  
   }
  
   CVframe =cvRetrieveFrame(capture);           // retrieve the captured frame
  
  
  
   /* always check */
  
   if (!CVframe)
  
   {
  
    printf("No CV frame captured!\n");
  
    cin.get();
  
   }
  
  
  
   /* resize buffer for current frame */
  
   IplImage* destination = cvCreateImage(cvSize(w, h), CVframe->depth, CVframe->nChannels);
  
  
  
   //use cvResize to resize source to a destination image
  
   cvResize(CVframe, destination);
  
  
  
   IplImage* redchannel = cvCreateImage(cvGetSize(destination), 8, 1);
  
   IplImage* greenchannel = cvCreateImage(cvGetSize(destination), 8, 1);
  
   IplImage* bluechannel = cvCreateImage(cvGetSize(destination), 8, 1);
  
  
  
   cvSplit(destination, bluechannel, greenchannel, redchannel, NULL);
  
   for(int y = 0; y < destination->height; y++)
  
   {
  
    char* line = buffer + y * bytespan;
  
    for(int x = 0; x < destination->width; x++)
  
    {
  
     line[0] = cvGetReal2D(redchannel, y, x);
  
     line[1] = cvGetReal2D(greenchannel, y, x);
  
     line[2] = cvGetReal2D(bluechannel, y, x);
  
     line += 3;
  
    }
  
   }
  
   cvReleaseImage(&redchannel);
  
   cvReleaseImage(&greenchannel);
  
   cvReleaseImage(&bluechannel);
  
   cvReleaseImage(&destination);
  
  }

  So generally it captures a frame from device, creates a frame to resize into and copies it into buffer (RGB or YUV420P is requirement for me).

  So I wonder what I do wrong, because my function is way 2 cpu intensive, and what can be done to fix it ?

  Update :

  My function is runed in thread :

       void ThreadCaptureFrame()
  
      {
  
          while(1){
  
          t.restart();
  
          CaptureFrame((char *)frame->data[0], videoWidth, videoHeight, frame->linesize[0]);
  
          AVFrame* swap = frame;
  
          frame = readyFrame;
  
          readyFrame = swap;
  
          spendedTime = t.elapsed();
  
          if(spendedTime < desiredTime){
  
              Sleep(desiredTime - spendedTime);
  
          }
  
      }
  
   }

  which is started at the beginning of int main ( after some initialization) :

  boost::thread workerThread(ThreadCaptureFrame);

  So if it can it runs 24 times per second, it eats 28% of core quad. cam resolution I capture is like 320x240. So : how to optimize it ?

• avfilter : Add blue and violet noise generation filters

  19 juillet 2017, par George Boyle

  avfilter : Add blue and violet noise generation filters
  For the blue and violet noise, I took the pink and brown noise
  
  respectively and subtracted the offsets instead of adding them. When I
  
  eyeball the frequency spectrum of the resulting outputs it looks correct
  
  to me, i.e. the blue graph appears to be a mirror image of the pink, and
  
  the same can be said of the violet and the brown. I did not do anything
  
  else to confirm the correctness.
  

  • [DH] doc/filters.texi
  • [DH] libavfilter/asrc_anoisesrc.c

• Anomalie #2884 : un modèle doc dans une liste, interrompt l’énumération

  24 octobre 2012, par Bertrand Marne

  Je me rends compte que mon exemple est mal choisi, car en fait c’est avec le modèle doc (et non img) que je rencontre le souci : -# premier point -# second point -# troisième point