What are the problems that changes the fps in video processing? [closed]

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I am trying to detect a white color object in motion using OpenCV and OpenCL. The camera that i am using is my laptop camera of 30 fps. what i am observing is that at different locations I am getting a different fps, the camera and the code being the same. for Ex in my room when I execute the code i get a full fps of 30 while in the lab it is 22...please can anyone tell that what can be the probable reason for it and how it can be corrected...The code I have used is below...Thank You in advance...

#include <iostream>
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <opencv2\ocl\ocl.hpp>
#include <time.h>
#include <iostream>


using namespace cv;
using namespace std;

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

     time_t t= time(0);
    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;
    }

  namedWindow("Control", CV_WINDOW_AUTOSIZE); //create a window called "Control"

    int iLowH = 0;
   int iHighH = 255;

    int iLowS = 0; 
   int iHighS = 255;

    int iLowV = 0;
   int iHighV = 255;

    //Create trackbars in "Control" window
   cvCreateTrackbar("LowH", "Control", &iLowH, 255); //Hue (0 - 179)
   cvCreateTrackbar("HighH", "Control", &iHighH, 255);

    cvCreateTrackbar("LowS", "Control", &iLowS, 255); //Saturation (0 - 255)
   cvCreateTrackbar("HighS", "Control", &iHighS, 255);

    cvCreateTrackbar("LowV", "Control", &iLowV, 255); //Value (0 - 255)
   cvCreateTrackbar("HighV", "Control", &iHighV, 255);


  ocl::oclMat alpha;
    int fps=0;
    int cur=0;
    while (true)
    {

      fps++;
      t=time(0);
      struct tm *tmp = gmtime(&t);

      int h= (t/360) %24;
      int m= (t/60) %60;
      int s = t%60;
      if(cur !=s)
      {
        cout<<fps;
        fps=0;
        cur=s;
      }

      Mat imgOriginal;

      bool bSuccess = cap.read(imgOriginal); // read a new frame from video

       if (!bSuccess) //if not success, break loop
      {
         cout << "Cannot read a frame from video stream" << endl;
         break;
      }


      alpha.upload(imgOriginal);
          ocl::oclMat imgHSV;

      ocl::cvtColor(alpha, imgHSV, CV_RGB2HSV); //Convert the captured frame from BGR to HSV
        ocl::oclMat channel[4];
        ocl::split(alpha,channel);
            ocl::oclMat imgThresholded[2];

        ocl::threshold(channel[0], imgThresholded[0] , iLowH , 255 , 0 );
            ocl::threshold(channel[0], imgThresholded[1] , iHighH , 255 , 1 );
            ocl::bitwise_and(imgThresholded[0],imgThresholded[1],channel[0]);

        ocl::threshold(channel[1], imgThresholded[0] , iLowS , 255 , 0 );
        ocl::threshold(channel[1], imgThresholded[1] , iHighS , 255 , 1 );
        ocl::bitwise_and(imgThresholded[0],imgThresholded[1],channel[1]);

      ocl::threshold(channel[2], imgThresholded[0] , iLowV , 255 , 0 );
        ocl::threshold(channel[2], imgThresholded[1] , iHighV , 255 , 1 );
      ocl::bitwise_and(imgThresholded[0],imgThresholded[1],channel[2]);

      ocl::bitwise_and(channel[0],channel[1],imgThresholded[0]);
      ocl::bitwise_and(imgThresholded[0],channel[2],imgThresholded[1]);

      //morphological opening (remove small objects from the foreground)
        ocl::erode(imgThresholded[1], imgThresholded[1], getStructuringElement(MORPH_ELLIPSE, Size(5, 5)) );
      ocl::dilate( imgThresholded[1], imgThresholded[1], getStructuringElement(MORPH_ELLIPSE, Size(5, 5)) ); 

      //morphological closing (fill small holes in the foreground)
      ocl::dilate( imgThresholded[1], imgThresholded[1], getStructuringElement(MORPH_ELLIPSE, Size(5, 5)) ); 
        ocl::erode(imgThresholded[1], imgThresholded[1], getStructuringElement(MORPH_ELLIPSE, Size(5, 5)) );
      int c= ocl ...