tracking people using kalman filter

int main (int argc,char** argv ){
    IplImage *frame = 0;
    cvNamedWindow("src",1);
    cvNamedWindow("gray",1);
    CvCapture* capture =cvCaptureFromAVI("c:/dev/projects/opencv_test/kalman.avi");
    CvKalman *kalman = cvCreateKalman( 4, 2, 0 );

    CvRandState rng;
    cvRandInit( &rng, 0, 1, -1, CV_RAND_UNI );
    CvMat *x_k = cvCreateMat( 3, 1, CV_16UC1 );
    cvRandSetRange( &rng, 0, 0.1, 0 );
    rng.disttype = CV_RAND_NORMAL;
    cvRand( &rng, x_k );

    const float F[] = { 1, 0, 1, 0,
                       0, 1, 0, 1,
                       0, 0, 1, 0,
                       0, 0, 0, 1};

    memcpy( kalman->transition_matrix->data.fl, F, sizeof(F));
    const float H[] = { 1, 0, 0, 0,
                        0, 1, 0, 0};

    memcpy( kalman->measurement_matrix->data.fl, H, sizeof(H));
    const float Q[] = { 0.0005, 0, 0, 0,
                        0, 0.0005, 0, 0,
                        0, 0, 0.0005, 0,
                        0, 0, 0, 0.0005 };

    memcpy( kalman->process_noise_cov->data.fl, Q, sizeof(Q));
    const float R[] = { 0.1, 0,
                        0, 0.1,};

    memcpy( kalman->measurement_noise_cov->data.fl, R,sizeof(R));
    const float V[] = { 0, 0, 0, 0,
                        0, 0, 0, 0,
                        0, 0, 0, 0,
                        0, 0, 0, 0 };

    memcpy( kalman->error_cov_post->data.fl, V, sizeof(V));
    cvRand( &rng, kalman->state_post );
    CvMat* w_k = cvCreateMat( 2, 1, CV_16UC1 );
    CvMat* z_k = cvCreateMat( 2, 1, CV_32FC1 );
    cvZero( z_k );

    IplImage* imgwhite = NULL;

    while(cvGrabFrame(capture))
    {
        frame=cvRetrieveFrame(capture);
        int imgWidth=frame->width;
        int imgHeight=frame->height;
        IplImage *gray = cvCreateImage(cvSize(imgWidth,imgHeight),8,1);
        cvCvtColor(frame,gray,CV_BGR2GRAY);
        cvThreshold(gray,gray,150,255,CV_THRESH_BINARY);
        cvSmooth( gray, gray, CV_GAUSSIAN, 9, 9 );
        if(!frame)
            break;

        // If this is the first frame, we need to initialize it
        if(imgwhite== NULL)
        {
                imgwhite = cvCreateImage(cvGetSize(frame), 8, 3);
        }
        CvMoments *moments = (CvMoments*)malloc(sizeof(CvMoments));
        cvMoments(gray, moments, 1);
        
        // The actual moment values
        double moment10 = cvGetSpatialMoment(moments, 1, 0);
        double moment01 = cvGetSpatialMoment(moments, 0, 1);
        double area = cvGetCentralMoment(moments, 0, 0);
        
        // Holding the last and current ball positions
        static int posX ;
        static int posY ;
        
        int lastX = posX;
        int lastY = posY;
        
        posX = moment10/area;
        posY = moment01/area;
        if(lastX>0 && lastY>0 && posX>0 && posY>0)
        {
            //Print it out for debugging purposes
            printf("position (%d,%d)\n", posX, posY);
            int pt1=posX;
            int pt2=posY;
            int measurement[]={pt1,pt2};
            memcpy( z_k->data.fl, measurement,sizeof(measurement));
            cvKalmanCorrect( kalman, z_k );
            float measured_x = z_k->data.fl[0];
            float measured_y = z_k->data.fl[1];
            printf ("z_k: %f, %f", measured_x, measured_y);
            const CvMat* y_k = cvKalmanPredict( kalman, 0 );
            float predicted_x = y_k->data.fl[0];
            float predicted_y = y_k->data.fl[1];
            

            // if(lastX>0 && lastY>0 && posX>0 && posY>0)
            //{
                cvLine(imgwhite, cvPoint(posX, posY), cvPoint(lastX, lastY), cvScalar(0,255,0), 2);
                cvLine(frame,cvPoint(predicted_x,predicted_y), cvPoint(pt1,pt2), CV_RGB(0,255,255),2);
            //}
        }

        cvAdd(frame, imgwhite, frame);
        cvShowImage("src" ,frame);
        
        cvShowImage("gray",gray);
        
        
        if(cvWaitKey(100) == 27){
            break;
        }
    }

    //release all windows
    cvDestroyAllWindows();

}