Is there considerable overlap between the CV/Image Processing part of OpenCV and IPP ?
Yes, optimized ippCV and ippI functions can be called from some OpenCV functions. To enable it you shoul build OpenCV with the special define and have IPP in paths (see OpenCV readme).
I wanted to detect face from a web camera. I found an example of face detection in samples folder.But they have provided a wrapper class called as CIppiImage . I am retriving frame using open cv,so I am not able to figure out that How I will be able to convert Mat Image or IplImage to the type of CIppiImage