opencv + cuda how to record video from the screen at 64 fps?

Question

Good afternoon. At the moment I cannot find information on how to record video from the screen using opencv + cuda at 64 fps. I have some code that uses cpu but not gpu, so it's about 25 fps. Please help me find information.

#include <iostream>
#include <opencv2/opencv.hpp>
#include <opencv2/cudaarithm.hpp>
#include <opencv2/video.hpp>
#include "opencv2/imgproc.hpp"
#include "opencv2/highgui.hpp"
#include <Windows.h>

using namespace std;
using namespace cv;
using namespace cv::cuda;

Mat hwnd2mat(HWND hwnd)
{
HDC hwindowDC, hwindowCompatibleDC;

int height, width, srcheight, srcwidth;
HBITMAP hbwindow;
Mat src;
BITMAPINFOHEADER  bi;

hwindowDC = GetDC(hwnd);
hwindowCompatibleDC = CreateCompatibleDC(hwindowDC);
SetStretchBltMode(hwindowCompatibleDC, COLORONCOLOR);

RECT windowsize;    // get the height and width of the screen
GetClientRect(hwnd, &windowsize);

srcheight = windowsize.bottom;
srcwidth = windowsize.right;
height = windowsize.bottom / 1;  //change this to whatever size you want to resize to
width = windowsize.right / 1;

src.create(height, width, CV_8UC4);

// create a bitmap
hbwindow = CreateCompatibleBitmap(hwindowDC, width, height);
bi.biSize = sizeof(BITMAPINFOHEADER);    //http://msdn.microsoft.com/en-us/library/windows/window/dd183402%28v=vs.85%29.aspx
bi.biWidth = width;
bi.biHeight = -height;  //this is the line that makes it draw upside down or not
bi.biPlanes = 1;
bi.biBitCount = 32;
bi.biCompression = BI_RGB;
bi.biSizeImage = 0;
bi.biXPelsPerMeter = 0;
bi.biYPelsPerMeter = 0;
bi.biClrUsed = 0;
bi.biClrImportant = 0;

// use the previously created device context with the bitmap
SelectObject(hwindowCompatibleDC, hbwindow);
// copy from the window device context to the bitmap device context
StretchBlt(hwindowCompatibleDC, 0, 0, width, height, hwindowDC, 0, 0, srcwidth, srcheight, SRCCOPY); //change SRCCOPY to NOTSRCCOPY for wacky colors !
GetDIBits(hwindowCompatibleDC, hbwindow, 0, height, src.data, (BITMAPINFO*)&bi, DIB_RGB_COLORS);  //copy from hwindowCompatibleDC to hbwindow

// avoid memory leak
DeleteObject(hbwindow);
DeleteDC(hwindowCompatibleDC);
ReleaseDC(hwnd, hwindowDC);

return src;
}

int main(int argc, char** argv)
{
HWND hwndDesktop = GetDesktopWindow();
//namedWindow("output", WINDOW_NORMAL);
int key = 0;

while (1)
{
    Mat src = hwnd2mat(hwndDesktop);
    // you can do some image processing here
    imshow("output", src);
    key = waitKey(1);
}

}

how to record video from desktop at 64 fps? I tried to replace MAT with UMAT, which uses mostly gpu, but unfortunately it didn't work because of this function:

GetDIBits(hwindowCompatibleDC, hbwindow, 0, height, src.data, (BITMAPINFO*)&bi, DIB_RGB_COLORS);

Because the UMAT class has no variable data.

Edit: Good afternoon, I updated the hwnd2mat function for gpu, but it gives me a black screen for some reason. Help me please.

UMat hwnd2mat(HWND hwnd)
{
HDC hwindowDC, hwindowCompatibleDC;

int height, width, srcheight, srcwidth;
HBITMAP hbwindow;
UMat src;
BITMAPINFOHEADER  bi;

hwindowDC = GetDC(hwnd);
hwindowCompatibleDC = CreateCompatibleDC(hwindowDC);
SetStretchBltMode(hwindowCompatibleDC, COLORONCOLOR);

RECT windowsize;    // get the height and width of the screen
GetClientRect(hwnd, &windowsize);

srcheight = windowsize.bottom;
srcwidth = windowsize.right;
height = windowsize.bottom / 1;  //change this to whatever size you want to resize to
width = windowsize.right / 1;

src.create(height, width, CV_8UC4);

// create a bitmap
hbwindow = CreateCompatibleBitmap(hwindowDC, width, height);
bi.biSize = sizeof(BITMAPINFOHEADER);    //http://msdn.microsoft.com/en-us/library/windows/window/dd183402%28v=vs.85%29.aspx
bi.biWidth = width;
bi.biHeight = -height;  //this is the line that makes it draw upside down or not
bi.biPlanes = 1;
bi.biBitCount = 32;
bi.biCompression = BI_RGB;
bi.biSizeImage = 0;
bi.biXPelsPerMeter = 0;
bi.biYPelsPerMeter = 0;
bi.biClrUsed = 0;
bi.biClrImportant = 0;

// use the previously created device context with the bitmap
SelectObject(hwindowCompatibleDC, hbwindow);
// copy from the window device context to the bitmap device context
StretchBlt(hwindowCompatibleDC, 0, 0, width, height, hwindowDC, 0, 0, srcwidth, srcheight, SRCCOPY); //change SRCCOPY to NOTSRCCOPY for wacky colors !
GetDIBits(hwindowCompatibleDC, hbwindow, 0, height, src.u->data, (BITMAPINFO*)&bi, DIB_RGB_COLORS);  //copy from hwindowCompatibleDC to hbwindow

// avoid memory leak
DeleteObject(hbwindow);
DeleteDC(hwindowCompatibleDC);
ReleaseDC(hwnd, hwindowDC);

return src;
}

Answer 1

CUDA helps to accelerate processing functions, but cannot help in accelerating capture of desktop. In this case, bottleneck is the blit API you are using to capture the screen (GetDIBits). Since you seem to be having a Nvidia GPU, you should look at OS/driver level alternatives like mentioned here ( https://developer.nvidia.com/capture-sdk ).