OpenCV crop live feed from camera

How can I get properly one resolution feed from camera in OpenCV (640x320) but cut it into half and display only one half of the frame (320x240). So not to scale down, but to actually crop. I am using OpenCV 2.4.5, VS2010 and C++

This quite standard code gets 640x480 input resolution and I made some changes to crop resolution to 320x240. Should I use Mat instead of IplImage, and if so what would be the best way?

#include "stdafx.h"
#include <iostream>
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"

using namespace std;
char key;
int main()
{
    cvNamedWindow("Camera_Output", 1);    //Create window

    CvCapture* capture = cvCaptureFromCAM(1);  //Capture using camera 1 connected to system
    cvSetCaptureProperty( capture, CV_CAP_PROP_FRAME_WIDTH, 640 );
    cvSetCaptureProperty( capture, CV_CAP_PROP_FRAME_HEIGHT, 480 );

    while(1){ //Create loop for live streaming

        IplImage* framein = cvQueryFrame(capture); //Create image frames from capture

        /* sets the Region of Interest  - rectangle area has to be __INSIDE__ the image */
        cvSetImageROI(framein, cvRect(0, 0, 320, 240));

        /* create destination image  - cvGetSize will return the width and the height of ROI */
        IplImage *frameout = cvCreateImage(cvGetSize(framein),  framein->depth, framein->nChannels);

        /* copy subimage */
        cvCopy(framein, frameout, NULL);

        /* always reset the Region of Interest */
        cvResetImageROI(framein);

        cvShowImage("Camera_Output", frameout);   //Show image frames on created window

        key = cvWaitKey(10);     //Capture Keyboard stroke
        if (char(key) == 27){
            break;      //ESC key loop will break.
        }
    }

    cvReleaseCapture(&capture); //Release capture.
    cvDestroyWindow("Camera_Output"); //Destroy Window
    return 0;
}