Correct YUV422 to RGB conversion

c++ image-processing opencv rgb yuv
Seb picture Seb · Nov 7, 2011 · Viewed 21.7k times · Source

I've been trying to tackle a YUV422 into a RGB conversion problem for about a week. I've visited many different websites and have gotten different formulas from each one. If anyone else has any suggestions I would be glad to hear about them. The formulas below give me an image with either and overall purple or a green hue in them. As of this moment I haven't been able to find a formula that allows me to get back a proper RGB image. I have include all my various chunks of code below.

    //for(int i = 0; i < 1280 * 720 * 3; i=i+3)
    //{
    //  /*m_RGB->imageData[i] = pData[i] + pData[i+2]*((1 - 0.299)/0.615);
    //  m_RGB->imageData[i+1] = pData[i] - pData[i+1]*((0.114*(1-0.114))/(0.436*0.587)) - pData[i+2]*((0.299*(1 - 0.299))/(0.615*0.587));
    //  m_RGB->imageData[i+2] = pData[i] + pData[i+1]*((1 - 0.114)/0.436);*/

    //  m_RGB->imageData[i] = pData[i] + 1.403 * (pData[i+1] - 128);
    //  m_RGB->imageData[i+1] = pData[i] + 0.344 * (pData[i+1] - 128) - 0.714 * (pData[i+2] - 128);
    //  m_RGB->imageData[i+2] = pData[i] + 1.773 * (pData[i+2] - 128);
    //}

    for(int i = 0, j=0; i < 1280 * 720 * 3; i+=6, j+=4)
    {
        /*m_RGB->imageData[i] = pData[j] + pData[j+3]*((1 - 0.299)/0.615);
        m_RGB->imageData[i+1] = pData[j] - pData[j+1]*((0.114*(1-0.114))/(0.436*0.587)) - pData[j+3]*((0.299*(1 - 0.299))/(0.615*0.587));
        m_RGB->imageData[i+2] = pData[j] + pData[j+1]*((1 - 0.114)/0.436);
        m_RGB->imageData[i+3] = pData[j+2] + pData[j+3]*((1 - 0.299)/0.615);
        m_RGB->imageData[i+4] = pData[j+2] - pData[j+1]*((0.114*(1-0.114))/(0.436*0.587)) - pData[j+3]*((0.299*(1 - 0.299))/(0.615*0.587));
        m_RGB->imageData[i+5] = pData[j+2] + pData[j+1]*((1 - 0.114)/0.436);*/

        /*m_RGB->imageData[i] = pData[j] + 1.403 * (pData[j+3] - 128);
        m_RGB->imageData[i+1] = pData[j] + 0.344 * (pData[j+1] - 128) - 0.714 * (pData[j+3] - 128);
        m_RGB->imageData[i+2] = pData[j] + 1.773 * (pData[j+1] - 128);
        m_RGB->imageData[i+3] = pData[j+2] + 1.403 * (pData[j+3] - 128);
        m_RGB->imageData[i+4] = pData[j+2] + 0.344 * (pData[j+1] - 128) - 0.714 * (pData[j+3] - 128);
        m_RGB->imageData[i+5] = pData[j+2] + 1.773 * (pData[j+1] - 128);*/

        BYTE Cr = pData[j+3] - 128;
        BYTE Cb = pData[j+1] - 128;
        /*m_RGB->imageData[i] = pData[j] + Cr + (Cr >> 2) + (Cr >> 3) + (Cr >> 5);
        m_RGB->imageData[i+1] = pData[j] - ((Cb >> 2) + (Cb >> 4) + (Cb >> 5)) - ((Cr >> 1) + (Cr >> 3) + (Cr >> 4) + (Cr >> 5));
        m_RGB->imageData[i+2] = pData[j] + Cb + (Cb >> 1) + (Cb >> 2) + (Cb >> 6);
        m_RGB->imageData[i+3] = pData[j+2] + Cr + (Cr >> 2) + (Cr >> 3) + (Cr >> 5);
        m_RGB->imageData[i+4] = pData[j+2] - ((Cb >> 2) + (Cb >> 4) + (Cb >> 5)) - ((Cr >> 1) + (Cr >> 3) + (Cr >> 4) + (Cr >> 5));
        m_RGB->imageData[i+5] = pData[j+2] + Cb + (Cb >> 1) + (Cb >> 2) + (Cb >> 6);*/

        /*int R1 = clamp(1 * pData[j] + 0 * Cb + 1.4 * Cr, 0, 255), R2 = clamp(1 * pData[j+2] + 0 * Cb + 1.4 * Cr, 0, 255);
        int G1 = clamp(1 * pData[j] - 0.343 * Cb - 0.711 * Cr, 0, 255), G2 = clamp(1 * pData[j+2] - 0.343 * Cb - 0.711 * Cr, 0, 255);
        int B1 = clamp(1 * pData[j] + 1.765 * Cb + 0 * Cr, 0, 255), B2 = clamp(1 * pData[j+2] + 1.765 * Cb + 0 * Cr, 0, 255);*/

        /*int R1 = clamp(pData[j] + 1.403 * (pData[j+3] - 128), 0, 255), R2 = clamp(pData[j+2] + 1.403 * (pData[j+3] - 128), 0, 255);
        int G1 = clamp(pData[j] + 0.344 * (pData[j+1] - 128) - 0.714 * (pData[j+3] - 128), 0, 255), G2 = clamp(pData[j+2] + 0.344 * (pData[j+1] - 128) - 0.714 * (pData[j+3] - 128), 0, 255);
        int B1 = clamp(pData[j] + 1.773 * (pData[j+1] - 128), 0, 255), B2 = clamp(pData[j+2] + 1.773 * (pData[j+1] - 128), 0, 255);*/

        int R1 = clamp((298 * (pData[j] - 16) + 409 * (pData[j+3] - 128) + 128) >> 8, 0, 255), R2 = clamp((298 * (pData[j+2] - 16) + 409 * (pData[j+3] - 128) + 128) >> 8, 0, 255);
        int G1 = clamp((298 * (pData[j] - 16) - 100 * (pData[j+1] - 128) - 208 * (pData[j+3] - 128) + 128) >> 8, 0, 255), G2 = clamp((298 * (pData[j+2] - 16) - 100 * (pData[j+1] - 128) - 208 * (pData[j+3] - 128) + 128) >> 8, 0, 255);
        int B1 = clamp((298 * (pData[j] - 16) + 516 * (pData[j+1] - 128) + 128) >> 8, 0, 255), B2 = clamp((298 * (pData[j+2] - 16) + 516 * (pData[j+1] - 128) + 128) >> 8, 0, 255);

        //printf("R: %d, G: %d, B: %d, R': %d, G': %d, B': %d \n", R1, G1, B1, R2, G2, B2);

        m_RGB->imageData[i] = (char)R1;
        m_RGB->imageData[i+1] = (char)G1;
        m_RGB->imageData[i+2] = (char)B1;
        m_RGB->imageData[i+3] = (char)R2;
        m_RGB->imageData[i+4] = (char)G2;
        m_RGB->imageData[i+5] = (char)B2;

        /*m_RGB->imageData[i] = (char)(clamp(1.164 * (pData[j] - 16) + 1.793 * (Cr), 0, 255));
        m_RGB->imageData[i+1] = (char)(clamp(1.164 * (pData[j] - 16) - 0.534 * (Cr) - 0.213 * (Cb), 0, 255));
        m_RGB->imageData[i+2] = (char)(clamp(1.164 * (pData[j] - 16) + 2.115 * (Cb), 0, 255));
        m_RGB->imageData[i+3] = (char)(clamp(1.164 * (pData[j+2] - 16) + 1.793 * (Cr), 0, 255));
        m_RGB->imageData[i+4] = (char)(clamp(1.164 * (pData[j+2] - 16) - 0.534 * (Cr) - 0.213 * (Cb), 0, 255));
        m_RGB->imageData[i+5] = (char)(clamp(1.164 * (pData[j+2] - 16) + 2.115 * (Cb), 0, 255));*/
    }

Any help is greatly appreciated.

Answer

ronag picture ronag · Nov 7, 2011

Some clues to help you along:

You are confusing Cr with Cb.

Assuming UYVY/422 

Y1 = data[j+0];
Cr = data[j+1];
Y2 = data[j+2];
Cb = data[j+3];

Your conversion calculation are wierd, and incorrect for HD.

For SD

R = max(0, min(255, 1.164(Y - 16) + 1.596(Cr - 128)));
G = max(0, min(255, 1.164(Y - 16) - 0.813(Cr - 128) - 0.391(Cb - 128)));
B = max(0, min(255, 1.164(Y - 16) + 2.018(Cr - 128)));

For HD

R = max(0, min(255, 1.164(Y - 16) + 1.793(Cr - 128)));
G = max(0, min(255, 1.164(Y - 16) - 0.534(Cr - 128) - 0.213(Cb - 128)));
B = max(0, min(255, 1.164(Y - 16) + 2.115(Cr - 128)));

You could simply use ConvertFrame which is a part of the Decklink SDK.

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