CODEWITHSUNDEEP
c++c++11image-processingvideo-processingfile-handling
PPP123
PPP123

Reputation: 43

Converting yuv 4:2:0 file to Rgb not getting expected output

The logic I am using is that I am reading he yuv file in a buffer and using 3 pointers to point to the Y,U,V components. The image dimension is 1920*1080.

I am

But the video output is incorrect. The output is somewhat like black and white

#include "stdafx.h"
#include <string>
#include <stdio.h>

unsigned char* g_pcRGBbuffer;
unsigned char* g_pcYUVBuffer;

int _tmain(int argc, _TCHAR* argv[])
{
    int l_nSize = 1920 * 1080 * 1.5;

    g_pcYUVBuffer = new unsigned char[l_nSize];
    g_pcRGBbuffer = new unsigned char[1920 * 1080 * 3];
    FILE* fp_source;
    FILE* fp_rgb = NULL;
    int l_nY, l_nU, l_nV;
    double l_dR, l_dG, l_dB, l_ni;

    fp_source = fopen("D:\\Sample_1920x1080.yuv", "rb");
    // converting yuv file to rgb file
    if (fp_source)
    {
        fp_rgb = fopen("D:\\Sample_1920x1080.rgb", "wb+");
        while (!feof(fp_source))
        {
            fread(g_pcYUVBuffer, 1, l_nSize, fp_source);
            unsigned char* l_pcY = g_pcYUVBuffer;
            unsigned char* l_pcU = l_pcY + 1920 * 1080;
            unsigned char* l_pcV = l_pcU + ((1920 * 1080) / 4);
            unsigned char* l_pcRGBbuffer = g_pcRGBbuffer;

            for (l_ni = 0; l_ni < (1920 * 1080) / 4; l_ni++)
            {
                l_nY = l_pcY[0];
                l_nU = l_pcU[0];
                l_nV = l_pcV[0];

                l_dR = l_nY + 1.402 * (l_nV - 128);
                l_dG = l_nY - 0.34414 * (l_nU - 128) - 0.71414 * (l_nV - 128);
                l_dB = l_nY + 1.772 * (l_nU - 128);

                // This prevents colour distortions in  rgb image
                if (l_dR < 0)
                    l_dR = 0;
                else if (l_dR > 255)
                    l_dR = 255;
                if (l_dG < 0)
                    l_dG = 0;
                else if (l_dG > 255)
                    l_dG = 255;
                if (l_dB < 0)
                    l_dB = 0;
                else if (l_dB > 255)
                    l_dB = 255;

                // 1st pixel of RGB
                l_pcRGBbuffer[0] = l_dR;
                l_pcRGBbuffer[1] = l_dG;
                l_pcRGBbuffer[2] = l_dB;

                l_nY = l_pcY[1];
                l_nU = l_pcU[0];
                l_nV = l_pcV[0];

                l_dR = l_nY + 1.402 * (l_nV - 128);
                l_dG = l_nY - 0.34414 * (l_nU - 128) - 0.71414 * (l_nV - 128);
                l_dB = l_nY + 1.772 * (l_nU - 128);

                if (l_dR < 0)
                    l_dR = 0;
                else if (l_dR > 255)
                    l_dR = 255;
                if (l_dG < 0)
                    l_dG = 0;
                else if (l_dG > 255)
                    l_dG = 255;
                if (l_dB < 0)
                    l_dB = 0;
                else if (l_dB > 255)
                    l_dB = 255;

                // 2nd pixel of RGB
                l_pcRGBbuffer[3] = l_dR;
                l_pcRGBbuffer[4] = l_dG;
                l_pcRGBbuffer[5] = l_dB;

                l_nY = l_pcY[2];
                l_nU = l_pcU[0];
                l_nV = l_pcV[0];

                l_dR = l_nY + 1.402 * (l_nV - 128);
                l_dG = l_nY - 0.34414 * (l_nU - 128) - 0.71414 * (l_nV - 128);
                l_dB = l_nY + 1.772 * (l_nU - 128);

                if (l_dR < 0)
                    l_dR = 0;
                else if (l_dR > 255)
                    l_dR = 255;
                if (l_dG < 0)
                    l_dG = 0;
                else if (l_dG > 255)
                    l_dG = 255;
                if (l_dB < 0)
                    l_dB = 0;
                else if (l_dB > 255)
                    l_dB = 255;

                // 3rd pixel of RGB
                l_pcRGBbuffer[6] = l_dR;
                l_pcRGBbuffer[7] = l_dG;
                l_pcRGBbuffer[8] = l_dB;

                l_nY = l_pcY[3];
                l_nU = l_pcU[0];
                l_nV = l_pcV[0];

                // l_dR = 1.164*(l_nY-16 ) + 1.596*(l_nV-128 );
                // l_dG = 1.164*(l_nY-16 ) - 0.813*(l_nV-128 ) - 0.391*(l_nU-128);
                // l_dB = 1.164*(l_nY-16 ) + 2.018*(l_nU-128 );

                l_dR = l_nY + 1.402 * (l_nV - 128);
                l_dG = l_nY - 0.34414 * (l_nU - 128) - 0.71414 * (l_nV - 128);
                l_dB = l_nY + 1.772 * (l_nU - 128);

                if (l_dR < 0)
                    l_dR = 0;
                else if (l_dR > 255)
                    l_dR = 255;
                if (l_dG < 0)
                    l_dG = 0;
                else if (l_dG > 255)
                    l_dG = 255;
                if (l_dB < 0)
                    l_dB = 0;
                else if (l_dB > 255)
                    l_dB = 255;

                // 4th pixel of RGB
                l_pcRGBbuffer[9] = l_dR;
                l_pcRGBbuffer[10] = l_dG;
                l_pcRGBbuffer[11] = l_dB;

                l_pcY += 4;
                l_pcU += 1;
                l_pcV += 1;
                l_pcRGBbuffer += 12;
            }

            fwrite(g_pcRGBbuffer, 1, 1920 * 1080 * 3, fp_rgb);
        }

        printf("Video converted to rgb file \n ");
    }
    else
    {
        printf("fail\n");
    }

    fclose(fp_rgb);
    fclose(fp_source);
    return 0;
}

Upvotes: 1

Views: 1242

Answers (1)

PPP123
PPP123

Reputation: 43

Actually YUV 4:2:0 planar stores all Y pixels first,then U pixels,then V pixels To extract correct pixels use the following forumla:

//Refer wikipedia for further details
size.total = size.width * size.height;
 y = yuv[position.y * size.width + position.x];
 u = yuv[(position.y / 2) * (size.width / 2) + (position.x / 2) + size.total];
 v = yuv[(position.y / 2) * (size.width / 2) + (position.x / 2) + size.total +           (size.total / 4)];

YUV2RGBTestApp2.cpp : Defines the entry point for the console application.

#include "stdafx.h"
#include <string>
#include <stdio.h>

unsigned char *g_pcRGBbuffer;
unsigned char *g_pcYUVBuffer;

int  _tmain(int argc, _TCHAR* argv[])
{
    int l_nSize = 1920 * 1080 * 1.5;
    g_pcYUVBuffer = new unsigned char[l_nSize];
    g_pcRGBbuffer = new unsigned char[1920 * 1080 * 3];
    FILE *fp_source;
    FILE *fp_rgb = NULL;
    int l_ny, l_nu, l_nv, l_ni, RGBval;
    int l_dr, l_dg, l_db;
    fp_source = fopen("D:\\Sample_1920x1080.yuv", "rb");
    int l_nj;


//converting yuv file to rgb file
     if (fp_source) {
          fp_rgb = fopen("D:\\Sample_1920x1080.rgb", "wb");
          while (!feof(fp_source))
            {
                fread(g_pcYUVBuffer, 1, l_nSize, fp_source);
                unsigned char *l_pcRGBbuffer = g_pcRGBbuffer;
                for (int j = 0; j < 1080; j++)
                {
                   for (int i = 0; i<1920; i++)
                    {
                   /*
                          Position  for y,u,v components for yuv planar 4:2:0  
                          Refer wikipedia for further reference  
                            
                   */
                      int Y = g_pcYUVBuffer[j * 1920 + i];
                      int U = g_pcYUVBuffer[((j / 2) * 960) + (i / 2) + (1920 * 1080)];
                      int V = g_pcYUVBuffer[((j / 2) * 960) + (i / 2) + (1920 * 1080) + ((1920 * 1080) / 4)];

                       int R = 1.164*(Y - 16) + 1.596*(V - 128);
                       int G = 1.164*(Y - 16) - 0.813*(V - 128) - 0.391*(U - 128);
                       int B = 1.164*(Y - 16) + 2.018*(U - 128);



                       if (R>255)R = 255;
                       if (R<0)R = 0;
                       if (G>255)G = 255;
                       if (G<0)G = 0;
                       if (B>255)B = 255;
                       if (B<0)B = 0;


                       l_pcRGBbuffer[0] = R;
                       l_pcRGBbuffer[1] = G;
                       l_pcRGBbuffer[2] = B;
                       l_pcRGBbuffer += 3;

                }
             }
        
            fwrite(g_pcRGBbuffer, 1, 1920 * 1080 * 3, fp_rgb);
        }

        printf("Video converted to rgb file \n ");

     }
     else {
        printf("fail\n");
   }

    fclose(fp_rgb);
    fclose(fp_source);
    return 0;
}

Upvotes: 1

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