func (capture *Capture) GrabFrame() bool {
	rv := C.cvGrabFrame((*C.CvCapture)(capture))
	return (rv != C.int(0))
}
func (capture *Capture) GrabFrame() bool {
	rv := C.cvGrabFrame((*C.CvCapture)(capture))
	return (rv != C.int(0))
}
/* grab a frame, return 1 on success, 0 on fail.
this function is thought to be fast               */