Increasing fps of pi camera using OpenCV C++ implementation

Question

I am using a NOIR Pi camera for my Raspberry Pi 3 module. I plan to run some high fps image processing algo using openCV in a C++ environment. However, I cant seem to obtain the video stream in a high enough fps. Setting CV_CAM_PROPS_FPS using openCV's VideoCapture class doesn't seem to do anything to the actual fps of the camera.

Is there a way I can adjust the FPS of the camera to 90fps within the cpp file or externally from the console? I don't mind reducing the resolution of the video.

[Edit]

Here is the code i am using

#include "stdio.h"
#include "opencv2/opencv.hpp"

using namespace cv;

int main(int, char**)
{

 std::cout << "Init Program 2\n";

 VideoCapture cap(0); // open the default camera

if(!cap.isOpened())  // check if we succeeded
 {        
std::cout << "Camera Init Fail\n";
return -1;
 }

std::cout << "Camera Init Successful\n";
std::cout << "Setting parameters..\n";

std::cout <<"\t[PARAM_FPS] ";
if(!cap.set(CV_CAP_PROP_FPS,15)){
     std::cout <<"SUCCESS\n";
}else{
     std::cout <<"FAIL\n";
}

std::cout <<"\t[PARAM_FRAME_WIDTH] ";
if(!cap.set(CV_CAP_PROP_FRAME_WIDTH,320)){
     std::cout <<"SUCCESS\n";
}else{
     std::cout <<"FAIL\n";
}

std::cout <<"\t[PARAM_FRAME_HEIGHT] ";
if(!cap.set(CV_CAP_PROP_FRAME_HEIGHT,240)){
     std::cout <<"SUCCESS\n";
}else{
     std::cout <<"FAIL\n";
}

int nFPS = cap.get(CV_CAP_PROP_FPS);
std::cout << "Loaded FPS : " << nFPS << "\n";


namedWindow("show",1);
for(;;)
{
    Mat frame;
    cap >> frame; // get a new frame from camera
    imshow("show", frame);
    if(waitKey(1) >= 0) break;

}
// the camera will be deinitialized automatically in VideoCapture destructor
return 0;
 }

[Solved]

The setting the FPS after setting the width and height seems to do the trick. That makes sense because a higher resolution image will cause a significant drop in the FPS. Therefore every time you change the geometry feature, the FPS will reset by default.

Answer 1

As suggested in the comments, I think you need to set the frame geometry first and then set the frame-rate afterwards.

std::cout <<"\t[PARAM_FRAME_WIDTH] ";
if(!cap.set(CV_CAP_PROP_FRAME_WIDTH,320)){
     std::cout <<"SUCCESS\n";
}else{
     std::cout <<"FAIL\n";
}

std::cout <<"\t[PARAM_FRAME_HEIGHT] ";
if(!cap.set(CV_CAP_PROP_FRAME_HEIGHT,240)){
     std::cout <<"SUCCESS\n";
}else{
     std::cout <<"FAIL\n";
}

std::cout <<"\t[PARAM_FPS] ";
if(!cap.set(CV_CAP_PROP_FPS,15)){
     std::cout <<"SUCCESS\n";
}else{
     std::cout <<"FAIL\n";
}

int nFPS = cap.get(CV_CAP_PROP_FPS);
std::cout << "Loaded FPS : " << nFPS << "\n";

I think the reason is that if you try and set the (high) frane-rate first, it realises it cannot achieve the desired 90fps with the current (default) geometry, so it fails - whereas if you set the smaller, less demanding geometry first, it is then happy to aim for the higher frane-rate.