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• How to optimize YUV to RGB color conversion code

  1er février 2016, par user_12

  I have written a function to convert an image in YUV420P to RGB but it is taking 30 millisecond to convert an image (size : 1280 x 720) into RGB, but when I am using ffmpeg function ( as this) to convert YUV image into RGB its taking only 2 millisecond for the same image. What is the problem with my code ? How can I optimize the code that I have written ??
  My code is given below

   int step = origImage->widthStep;
  
   uchar *data = (uchar *)origImage->imageData; 
  
   int size = origImage->width * origImage->height;
  
   IplImage* img1 = cvCreateImage(cvGetSize(origImage), IPL_DEPTH_8U, 3);
  
  
  
      for (int i = 0; iheight; i++)
  
      {
  
        for (int j=0; jwidth; j++)
  
        {
  
          float Y = data[i*step + j];
  
          float U = data[ (int)(size + (i/2)*(step/2)  + j/2) ];
  
          float V = data[ (int)(size*1.25 + (i/2)*(step/2) + j/2)];
  
  
  
          float R = Y + 1.402 * (V - 128);
  
          float G = Y - 0.344 * (U - 128) - 0.714 * (V - 128);
  
          float B = Y + 1.772 * (U - 128);
  
  
  
  
  
          if (R < 0){ R = 0; } if (G < 0){ G = 0; } if (B < 0){ B = 0; }
  
          if (R > 255 ){ R = 255; } if (G > 255) { G = 255; } if (B > 255) { B = 255; }
  
  
  
          cvSet2D(img1, i, j,cvScalar(B,G,R));
  
        }
  
      }

• ffmpeg av_read_frame return error code -5

  17 septembre 2020, par Jianhua Zhu

  I use dll of ffmpeg read the USB camera, display the picture on the control, and save the image to the file. At first, the reading is normal. The sound and image can be saved. But after reading for a few minutes, data can not be read, av_read_frame return error code is - 5, and the camera is automatically turned off. Direct use ffmpeg.exe when I go to read the camera and save the file, it won't be a problem for hours. Anybody can you tell me how to return - 5 error code and how to deal with it ?
ffmpeg version is 4.2.3
The code like this :

  


  while (1)
{
  if ((ret = av_read_frame(m_pVidFmtCtx, dec_pkt)) == 0)
  {
    ret = avcodec_send_packet(m_pVidFmtCtx->streams[dec_pkt->stream_index]->codec, dec_pkt);
    while(ret >= 0)
    {
      ret = avcodec_receive_frame(m_pVidFmtCtx->streams[dec_pkt->stream_index]->codec, pframe);
      sws_scale(img_rgb_ctx, pframe->data, pframe->linesize, 0, cy, dstData, dstLinesize);
      var bitmap = new Bitmap(dstWidth, dstHeight, dstLinesize[0], PixelFormat.Format24bppRgb, convertedFrameBufferPtr);
    }
  }
  else
  {
    printf("Error code: %d", ret); // Here ret is -5
  }
}


  


• Linking to libx264 library from c code Ubuntu

  30 janvier 2012, par Martin Conaghan

  I'm trying to write a small C application which uses the x264 API, and I'm having problems compiling the code with a link to the x264 libaray.

  In the /project/ directory there are two sub-folders :
  /project/mycode/ and
  /project/x264-snapshot-20120120-2245.

  I have installed x264 in the latter subdirectory using ./configure and then 'make'. As such the library I think I want to link to is /project/x264-snapshot-20120120-2245/libx264.a

  In /project/mycode/ I have a single source code file (prototype.c), which has the following imports :

  #include 
  
  #include 
  
  #include "../x264-snapshot-20120120-2245/x264_config.h"
  
  #include "../x264-snapshot-20120120-2245/x264.h"

  As expected, if I try to compile without linking to the x264 library, I get an error :

  /project/mycode: gcc -o prototype prototype.c
  
  /tmp/cc5NwRTp.o: In function `main':
  
  prototype.c:(.text+0x6c): undefined reference to `x264_param_default_preset'
  
  prototype.c:(.text+0xf6): undefined reference to `x264_param_apply_profile'
  
  collect2: ld returned 1 exit status

  So I try to link the library I mentioned above, but it isn't found :

  /project/mycode: gcc -o prototype prototype.c -I../x264-snapshot-20120120-2245/ -llibx264.a
  
  /usr/bin/ld: cannot find -llibx264.a
  
  collect2: ld returned 1 exit status

  I've tried a few variations, like :

  gcc -o prototype prototype.c -I../x264-snapshot-20120120-2245/ -l ../x264-snapshot-20120120-2245/libx264.a
  
  gcc -o prototype prototype.c -I../x264-snapshot-20120120-2245/ -llibx264
  
  gcc -I ../x264-snapshot-20120120-2245/ -llibx264.a -o prototype prototype.c

  As is probably obvious by now, I'm fairly new to this, so I'm hoping there is an easy solution