Raspberry Pi OpenCv C++ low frame rate - c++

Question

I am using opencv on my raspberry pi 2 B+ to do real time image processing. I am using raspberry pi's camera and have installed V4l2 driver prior to starting image processing.
The problem is that I am getting about 2-3 fps with a delay of about 3 seconds.I am doing a real-time application and am unable to achieve it due to these constraints. Also,when I try to set my frame rate and resolution i get the following errors:
VIDEOIO ERROR: V4L/V4L2 VIDIOC_CROPCAP
VIDEOIO ERROR: setting property #16 is not supported
VIDEOIO ERROR: setting propert #5 is not supported
What can be the possible reason for this problem?
Here is my code:
#include <opencv2/opencv.hpp>
#include "opencv2/highgui/highgui.hpp"
#include <stdio.h>
using namespace cv;
using namespace std;
int main( int argc, char** argv ) {
namedWindow("Camera",WINDOW_AUTOSIZE);
VideoCapture cap;
cap.open(0);
if(!cap.isOpened())
{
cout<<"Camera is not accessible"<<endl;
}
int width,length;
double fps;
fps=60;
cap.set(CV_CAP_PROP_CONVERT_RGB,false);
cap.set(CV_CAP_PROP_FPS,fps);
cap.set(CV_CAP_PROP_FRAME_HEIGHT,240);
cap.set(CV_CAP_PROP_FRAME_WIDTH,320);
Mat frame;
while(1)
{
cap>>frame;
fps = cap.get(CV_CAP_PROP_FPS);
width = cap.get(CAP_PROP_FRAME_WIDTH);
length = cap.get(CAP_PROP_FRAME_HEIGHT);
cout<<fps<<endl<<width<<endl<<length<<endl;
imshow("Camera",frame);
waitKey(33);
}
}