QVideoSink and QCamera very slow

Hi,

Found very slow QCamera and QVideoSink working. Not possible to use it.   Subscription to QVideoSink::videoFrameChanged catastrofically slowdowns application.
On Android : I have two sources on the screen: avi video (megamind.avi from OpenCV as example) and QT camera. While first source played - all ok, but if I run camera - avi goes slow because application slowdowns.
On windows: Qt camera very slow (6x times) against builtin OpenCV camera. This is checked in windows task manager.
We have QVideoSink again unworkable. If on Win this behavior not so dramatically affects speed (1% cpu with OpenCV Camera  vs  6% with QCamera), but on Android application speed reduced to x10 times.

connect(this, &QVideoSink::videoFrameChanged, this, &QTCam::hvideoFrameChanged);// <- catastrofically slowdowns (may be x10) application
// without this subscription line - application works fast as expected
m_captureSession.setVideoSink(this);

void hvideoFrameChanged(const QVideoFrame &frame)
{// no code here, only this empty :
videoframeReady=true;
#ifdef Q_OS_ANDROID
static_cast<QVideoFrame>(frame).map(QVideoFrame::ReadOnly); // <- problem here ? or inside QT camera engine ? or inside subscription engine ?
#endif
}