Using Hue and Saturation to calculate Backprojection of an object

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In OpenCV it is possible to calculate the backprojection of a selected area using only the Hue component in the HSV image (CamSHIFT example). I am trying to do the same thing but using both the Hue and Saturation components to compute the backprojection. I am not sure whether I am doing it correctly. Below is my code,

The functions that I am not to sure about are

• int ch[] = { 0,0, 1,0}; // here from what I understand, for the variable fromTo needed in the mixChannels function, does this hsv[0]->hue[0], hsv[0]->saturation[1]
• mixChannels(&hsv, 1, out, 2, ch, 2); // from what I understand should split, hue and saturation from hsv
• calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);

If someone has done something similar, could you please advise.

\\code

Mat backProjectObject(Mat frame, Point pnt){

   int hsize = 16, ssize = 16;
   int hdims[] = { hsize, ssize };
   float h_ranges[] = { 0,180 };
   float s_ranges[] = { 0,255 };
   const float* ranges[] = { h_ranges, s_ranges };

   Mat hsv, hue, saturation, mask, histimg = Mat::zeros(200, 320, CV_8UC3);
   MatND hist, backproj;

   Rect selection;
   int vmin = 10, vmax = 256, smin = 30;

   cvtColor(frame, hsv, CV_BGR2HSV);

   selection.x = pnt.x; //selected center for the area
   selection.y = pnt.y; //selected center for the area
   selection.width = 20; //selected center for the area
   selection.height = 20; //selected center for the area

   selection &= Rect(0, 0, frame.cols, frame.rows);

   int _vmin = vmin, _vmax = vmax;

   inRange(hsv, Scalar(0, smin, MIN(_vmin,_vmax)), Scalar(180, 256, MAX(_vmin, _vmax)), mask);
   hue.create(hsv.size(), hsv.depth());
   saturation.create(hsv.size(), hsv.depth());
   Mat out[] = { hue, saturation };
   int ch[] = { 0,0, 1,0};
   Mat planes[2][2];

   mixChannels(&hsv, 1, out, 2, ch, 2);

   planes[0][0] = hue; 
   planes[0][1] = saturation;

   Mat roi1(hue, selection), roi2(saturation, selection), maskroi(mask, selection);

   planes[1][0] = roi1; //selected template
   planes[1][1] = roi2; //selected template        

   calcHist(planes[1], 1, 0, maskroi, hist, 1, hdims, ranges);
   normalize(hist, hist, 0, 255, CV_MINMAX);

   calcBackProject(planes[0], 1, 0, hist, backproj, ranges);
   backproj &= mask;
   threshold( backproj, backproj, 250, 255,0 );

   return backproj;

}