Cascade Classifier

I am using Cascade Classifier to detect objects in a video stream. I load the .xml classifier file that I have trained before. Then I use detectMultiCsale to perform the detection but the problem is when I use detectMultiScale to perform the detection it cause my detection delay and lag. May I know have any other method to use .xml file to detect the object using cascade classifier? I am using opencv 3.3.0 and I using c++ in my coding. Anyone can help me?Thank you.