Using opencv + viola jones running slow - c++

Question

I am trying to implement Face detection viola jones classifier using opencv cascade. This is the code i am using:
int main( ){
SYSTEMTIME tm;
GetLocalTime(&tm);
printf("Date: %02d.%02d.%d, %02d:%02d:%02d:%02d\n", tm.wDay, tm.wMonth, tm.wYear, tm.wHour, tm.wMinute, tm.wSecond, tm.wMilliseconds);
//CString t = CTime::GetCurrentTime().Format("%H:%M:%S:%MS");
Mat image;
Mat frame_gray;
image = imread("test.jpg", CV_LOAD_IMAGE_COLOR);
namedWindow( "window1", 1 ); imshow( "window1", image );
// Load Face cascade (.xml file)
CascadeClassifier face_cascade;
face_cascade.load( "cascades.xml" );
cvtColor( image, frame_gray, CV_BGR2GRAY );
equalizeHist( frame_gray, frame_gray );
GetLocalTime(&tm);
printf("Date: %02d.%02d.%d, %02d:%02d:%02d:%02d\n", tm.wDay, tm.wMonth, tm.wYear, tm.wHour, tm.wMinute, tm.wSecond, tm.wMilliseconds);
float pyramidScale = 1.5f;
// Detect faces
std::vector<Rect> faces;
face_cascade.detectMultiScale( frame_gray, faces, pyramidScale, 3, 0, Size(20, 20), Size(50, 50));
GetLocalTime(&tm);
printf("Date: %02d.%02d.%d, %02d:%02d:%02d:%02d\n", tm.wDay, tm.wMonth, tm.wYear, tm.wHour, tm.wMinute, tm.wSecond, tm.wMilliseconds);
// Draw circles on the detected faces
for( int i = 0; i < faces.size(); i++ )
{
Point center( faces[i].x + faces[i].width*0.5, faces[i].y + faces[i].height*0.5 );
ellipse( image, center, Size( faces[i].width*0.5, faces[i].height*0.5), 0, 0, 360, Scalar( 255, 255, 255 ), 4, 8, 0 );
}
imshow( "Detected Face", image );
SYSTEMTIME tm1;
GetLocalTime(&tm);
printf("Date: %02d.%02d.%d, %02d:%02d:%02d:%02d\n", tm.wDay, tm.wMonth, tm.wYear, tm.wHour, tm.wMinute, tm.wSecond, tm.wMilliseconds);
//cout<< "Time : "<<tm.wHour<<":"<<tm.wMinute << ":"<< tm.wSecond << ":" << tm.wMilliseconds << "\n";
waitKey(0);
return 0;
}
The problem is it says this is viola jones implementation in opencv and usually takes 30fps to run (from the author side) but its taking 6 seconds to run a normal HD image for face detection of around 1920x1080. I wanted to ask is the implementation right or is there any problem with the way i am implementing the method and is there any way i can make it faster ? The cascade.xml is a file i trained using sample images. Thank you.