How to set camera fps in opencv? - c++

Question

I'm using a webcam supporting 1280 x 720 # 60 fps.
My computer environment is intel i5-4690K and Windows7, Visual studio 2015, opencv 3.1
When I run the webcam in Kinovea(0.85.15, https://www.kinovea.org/), the camera run at the 1280 x 720 # 60fps.
But, In Visual studio with Opencv, it isn't work # 60 fps.
It just work only 12~15 fps.
My code for checking the camera fps is below.
#include <stack>
#include <iostream>
#include <math.h>
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/videoio.hpp"
#include <opencv2/video.hpp>
#include "opencv2/imgcodecs.hpp"
#include <time.h>
using namespace cv;
using namespace std;
int keyboard;
int main(int argc, char** argv)
{
VideoCapture cap(0); //capture the video from web cam
if (!cap.isOpened()) // if not success, exit program
{
cout << "Cannot open the web cam" << endl;
return -1;
}
cap.set(CV_CAP_PROP_FRAME_WIDTH, 1280);
cap.set(CV_CAP_PROP_FRAME_HEIGHT, 720);
while ((char)keyboard != 'q' && (char)keyboard != 27)
{
Mat imgOriginal;
Mat ROOI;
clock_t a = clock();
bool bSuccess = cap.read(imgOriginal);
if (!bSuccess)
{
cout << "Cannot read a frame from video stream" << endl;
break;
}
printf("Captue Time : %f\n", double(clock() - a) / double(CLOCKS_PER_SEC));
imshow("Original", imgOriginal);
if (waitKey(1) == 27)
{
cout << "esc key is pressed by user" << endl;
break;
}
}
return 0;
}
In above code. I check the "Capture Time" and it was usually records 0.07s ~ 0.09s.
So, I attempt to VideoCapture::set(CV_CAP_PROP_FPS, 60), but it isn't work.
(When I get the FPS using the code VideoCapture::get(CV_CAP_PROP_FPS), it return value 0.)
How can I control the webcam FPS?
Thanks.

Answer 1

When I modify my code like below, it works # 60 fps.
#include <stack>
#include <iostream>
#include <math.h>
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/videoio.hpp"
#include <opencv2/video.hpp>
#include "opencv2/imgcodecs.hpp"
#include <time.h>
using namespace cv;
using namespace std;
int keyboard;
int main(int argc, char** argv)
{
VideoCapture cap(0); //capture the video from web cam
if (!cap.isOpened()) // if not success, exit program
{
cout << "Cannot open the web cam" << endl;
return -1;
}
cap.set(CV_CAP_PROP_FOURCC, CV_FOURCC('M', 'J', 'P', 'G'));
cap.set(CV_CAP_PROP_FRAME_WIDTH, 1280);
cap.set(CV_CAP_PROP_FRAME_HEIGHT, 720);
while ((char)keyboard != 'q' && (char)keyboard != 27)
{
Mat imgOriginal;
Mat ROOI;
clock_t a = clock();
bool bSuccess = cap.read(imgOriginal);
if (!bSuccess)
{
cout << "Cannot read a frame from video stream" << endl;
break;
}
printf("Captue Time : %f\n", double(clock() - a) / double(CLOCKS_PER_SEC));
imshow("Original", imgOriginal);
if (waitKey(1) == 27)
{
cout << "esc key is pressed by user" << endl;
break;
}
}
return 0;
}
The key for camera working # 60 fps is
cap.set(CV_CAP_PROP_FOURCC, CV_FOURCC('M', 'J', 'P', 'G'));
My camera works #60 fps in MJPG mode. So I add above code, it works fine!

Answer 2

You could try setting the camera's frame rate outside of OpenCV, e.g. on Linux you can control UVC cameras (Logitech, etc.) using libwebcam, and uvcdynctrl in particular.