OpenCV Camera Low FPS

1

Hello, I was using OpenCV 4.5.1 to measure the FPS of my camera and I found the actual FPS measured is way below my expectation. The code I used for measurement is from How to find frame rate or frames per second (fps) in OpenCV ( Python / C++ ) ? | Learn OpenCV

#include "opencv2/opencv.hpp"
#include <time.h>

using namespace cv;
using namespace std;

int main(int argc, char** argv)
{

    // Start default camera
    VideoCapture video(0);

    // With webcam get(CV_CAP_PROP_FPS) does not work.
    // Let's see for ourselves.

    // double fps = video.get(CV_CAP_PROP_FPS);
    // If you do not care about backward compatibility
    // You can use the following instead for OpenCV 3
    double fps = video.get(CAP_PROP_FPS);
    cout << "Frames per second using video.get(CAP_PROP_FPS) : " << fps << endl;

    // Number of frames to capture
    int num_frames = 120;

    // Start and end times
    time_t start, end;

    // Variable for storing video frames
    Mat frame;

    cout << "Capturing " << num_frames << " frames" << endl ;

    // Start time
    time(&start);

    // Grab a few frames
    for(int i = 0; i < num_frames; i++)
    {
        video >> frame;
    }

    // End Time
    time(&end);

    // Time elapsed
    double seconds = difftime (end, start);
    cout << "Time taken : " << seconds << " seconds" << endl;

    // Calculate frames per second
    fps  = num_frames / seconds;
    cout << "Estimated frames per second : " << fps << endl;

    // Release video
    video.release();
    return 0;
}

My camera is Logitech C930e, whose specification is 1080P 30FPS. Although the CAP_PROP_FPS shown is 30 FPS, the actual FPS I measured is only 13-15 FPS. I tried to build and switch the camera backend to V4L and FFMPEG. Switching to V4L was successful, but it did not improve the FPS. Switching to FFMPEG was not successful as I could not open the camera in OpenCV, even though I have linked the application to FFMPEG libraries including swscale, avformat, avcodec, and avutil.

I wonder if it is possible to increase the actual camera FPS to 30, or at least a value close to 30. Thank you.