How to using MediaPlayerElement to play rtsp stream in WinUI3 (in C++) in real-time within 200ms?

Question

I am using MediaPlayerElement to play rtsp stream in WinUI3 (in C++). Xaml code is like this:

MediaPlayerElement x:name="player" Source="rtsp://192.187.2.567" AutoPlay="true"

And I use "player().MediaPlayer().RealTimePlayback(TRUE)" in .cpp file when initializing the page.

The video stream delays for 350ms. But I want it to play in real-time and the latency is within 200ms. How can I further decrease the latency? which parameter can be set and how? Any ideas? Thanks a lot!