How to set camera fps with opencv

C++
,
8

Hi,
Thank you very much for you answers.
I read in other forum about the thread way but I want to try without thread.

what you do with waitKey there is a bad idea because of that . it’s best to use the lowest wait time possible here, which is 1 (or use pollKey() ). you don’t have to spend all idle time in waitKey . it only has to be entered periodically to keep the GUI window somewhat responsive.

Can you be more precise ?I did not understand everything this part cleary.

I modify my code to do something like this instead of using waitKey()

#include <chrono>
#include <ctime>
#include <opencv2/highgui.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/videoio.hpp>
#include <iostream>


int main(int argc, const char ** argv)
{
       cv::VideoCapture cap(0,200);
        int fpsCamera = 30;
int fpsCapture = 10;
        double fps2 = cap.get(cv::CAP_PROP_FPS);
        std::cout << "fps2 : " << fps2 << std::endl;

        if (!cap.isOpened())
        {
            cap.release();
            return -1;
        }

        std::chrono::time_point<std::chrono::high_resolution_clock>
                   prev_frame_time(std::chrono::high_resolution_clock::now());
        std::chrono::time_point<std::chrono::high_resolution_clock>
                           new_frame_time;

        cv::Mat frame;
        while (true)
        {
            if (videoCapture.read(frame) == false)
            {
                if (frame.empty())
                {
                	break;
                }
            }

            new_frame_time = std::chrono::high_resolution_clock::now();
            std::chrono::duration<double> duration1(new_frame_time - prev_frame_time);
            double fps = 1/duration1.count();
            std::cout << "fps : " << fps << std::endl;

            if(duration1.count() > 1/fpsCapture)
              {
                        	prev_frame_time = new_frame_time;
                  
            	imshow("Frame", frame);
            }

            int key = cv::waitKey(1000/fpsCamera );
            if (key % 256 == key_esc)
            {
            	break; // (27)escape key
            }
        }

        cap.release();
 return 0;
}

I don’t know if it’s the write way.