Embedding an OpenCV window into a Qt GUI

OpenCV recently upgraded its display window, when it is used in Qt. It looks very good, however I did not find any possibility for it to be embedded into an existing Qt GUI window. The only possibility seems to be the creation of a cvNamedWindow or cv::namedWindow, but it creates a free-floating independent window.

Is there any possibility to create that OpenCV window inside an existing GUI? All I could find on the OpenCV forums is an unanswered question, somewhat similar to my own.

There is a straight-forward possibility to show an OpenCV image in Qt, but it has two major problems:

1. it involves copying the image pixel by pixel, and it's quite slow. It has function calls for every pixel! (in my test application, if I create a video out of the images, and display it in a cvNamedWindow, it runs very smoothly even for multiple videos the same time, but if I go through the IplImage --> QImage --> QPixmap --> QLabel route, it has severe lag even for one single video)
2. I can't use those nice new controls of the cvNamedWindow with it.