How to retrieve the window ID to embed a video stream into this window?

Experts,

I am planning to put a gstreamer video stream into a LVGL window or canvas.
the code to do that with QT:

gst_video_overlay_set_window_handle (GST_VIDEO_OVERLAY (vsink), xwinid);

here, xwinid is a window handle from QT Qwidget.
But How can I get the similar winID from LVGL? I am using LVGL8.3, I can’t find any API to retrieve the window handle.

Thanks