how to covert Y,U,V buffer to one-dimensional array

Question

I'm trying to convert an hls file to jpeg. firstly, I used openh264 to convert HLS file to YUV. I got a two dimensional array containing Y, U, V buffer (*pData[3]). After that, I try to combine the three arrays into one to pass it to CompressYUYV2JPEG. here is how I convert:

for(i = 0; i < l; i++) {
        inbuf.push_back(yuvData[0][i]);
    }
    l = bufferInfo.UsrData.sSystemBuffer.iWidth*bufferInfo.UsrData.sSystemBuffer.iHeight/4;
    for(i = 0; i < l; i++) {
        inbuf.push_back(yuvData[1][i]);
    }
    l = bufferInfo.UsrData.sSystemBuffer.iWidth*bufferInfo.UsrData.sSystemBuffer.iHeight/4;
    for(i = 0; i < l; i++) {
        inbuf.push_back(yuvData[2][i]);
    }

but unfortunately, It doesn't produce the expected result. What is the proper way to convert 2-dimensional YUV array into a one-dimensional array?

Thomas Sablik · Accepted Answer · 2019-01-22T09:58:52.587

2

You need YUV422. That means YUYV. inbuf must be dividable by 4 for every input data. You can use

for(i = 0; i < l/2; i++) {
    inbuf.push_back(yuvData[0][2*i]);
    inbuf.push_back((yuvData[1][2*i] + yuvData[1][2*i + 1])/2);
    inbuf.push_back(yuvData[0][2*i + 1]);
    inbuf.push_back((yuvData[2][2*i] + yuvData[2][2*i + 1])/2);
}

In this code snippet all Y values are used but only the average of two Cr resp. Cb values are used. Of course the number of elements in each yuvData channel must be even. Otherwise you have to find a solution for the last element.

I just now saw that you use YUV420. Then you can use this snippet

for(i = 0; i < l/2; i++) {
    inbuf.push_back(yuvData[0][2*i]);
    inbuf.push_back(yuvData[1][i/2]);
    inbuf.push_back(yuvData[0][2*i + 1]);
    inbuf.push_back(yuvData[2][i/2]);
}

In this code all Y values are used once and all Cr resp. Cb values are used twice.

edited Jan 22 '19 at 09:58

answered Jan 22 '19 at 09:12

Thomas Sablik

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isn't YUV422 "YUYV-YUYV..."? but your code uses "YYUV-YYUV"? did you just make a mistake? – Pittie Jan 22 '19 at 09:22
ref: https://en.wikipedia.org/wiki/YUV#Y%E2%80%B2UV422_to_RGB888_conversion – Pittie Jan 22 '19 at 09:24
The comment in your link says "Each four bytes is two Y's, a Cb and a Cr." But in the code it is YUYV. You are right. I fixed it – Thomas Sablik Jan 22 '19 at 09:54
btw, how do I calculate 'l'? for(i = 0; i < l/2; i++) – Pittie Jan 22 '19 at 10:08
@Pittie It's the same `l` you had in your code snippet. `l` is the number of pixels `bufferInfo.UsrData.sSystemBuffer.iWidth*bufferInfo.UsrData.sSystemBuffer.iHeight` – Thomas Sablik Jan 22 '19 at 11:52

how to covert Y,U,V buffer to one-dimensional array

1 Answers1