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• Revision 8abd0c2a12 : Merge "Short circuit rate_block in block_rd_txfm."

  31 juillet 2015, par Aℓex Converse

  Changed Paths :
   Modify /vp9/encoder/vp9_rdopt.c

  
  
  Merge "Short circuit rate_block in block_rd_txfm."

• Convert individual pixel values from RGB to YUV420 and save the frame - C++

  24 mars 2014, par learner

  I have been working with RGB->YUV420 conversion for sometime using the FFmpeg library. Already tried the sws_scale functionality but its not working well. Now, I have decided to convert each pixel individually, using colorspace conversion formulae. So, following is the code that gets me few frames and allows me to access individual R,G,B values of each pixel :

  // Read frames and save first five frames to disk
  
      i=0;
  
      while((av_read_frame(pFormatCtx, &packet)>=0) && (i<5)) 
  
      {
  
          // Is this a packet from the video stream?
  
          if(packet.stream_index==videoStreamIdx) 
  
          {   
  
              /// Decode video frame            
  
              avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
  
  
  
              // Did we get a video frame?
  
              if(frameFinished) 
  
              {
  
                  i++;
  
                  sws_scale(img_convert_ctx, (const uint8_t * const *)pFrame->data,
  
                            pFrame->linesize, 0, pCodecCtx->height,
  
                            pFrameRGB->data, pFrameRGB->linesize);
  
  
  
                  int x, y, R, G, B;
  
                  uint8_t *p = pFrameRGB->data[0];
  
                  for(y = 0; y < h; y++)
  
                  {  
  
                      for(x = 0; x < w; x++) 
  
                      {
  
                          R = *p++;
  
                          G = *p++;
  
                          B = *p++;
  
                          printf(" %d-%d-%d ",R,G,B);
  
                      }
  
                  }
  
  
  
                  SaveFrame(pFrameRGB, pCodecCtx->width, pCodecCtx->height, i);
  
              }
  
          }
  
  
  
          // Free the packet that was allocated by av_read_frame
  
          av_free_packet(&packet);
  
      }

  I read online that to convert RGB->YUV420 or vice-versa, one should first convert to YUV444 format. So, its like : RGB->YUV444->YUV420. How do I implement this in C++ ?

  Also, here is the SaveFrame() function used above. I guess this will also have to change a little since YUV420 stores data differently. How to take care of that ?

  void SaveFrame(AVFrame *pFrame, int width, int height, int iFrame)
  
  {
  
      FILE *pFile;
  
      char szFilename[32];
  
      int  y;
  
  
  
      // Open file
  
      sprintf(szFilename, "frame%d.ppm", iFrame);
  
      pFile=fopen(szFilename, "wb");
  
      if(pFile==NULL)
  
          return;
  
  
  
      // Write header
  
      fprintf(pFile, "P6\n%d %d\n255\n", width, height);
  
  
  
      // Write pixel data
  
      for(y=0; ydata[0]+y*pFrame->linesize[0], 1, width*3, pFile);
  
  
  
      // Close file
  
      fclose(pFile);
  
  }

  Can somebody please suggest ? Many thanks !!!

• Merge remote-tracking branch ’ubitux/lavfi-mixed-short-long’

  11 avril 2013, par Michael Niedermayer

  Merge remote-tracking branch ’ubitux/lavfi-mixed-short-long’