How to use gstreamer vaapi download gpu frame to mainmemory

Question

I have a problem with gstreamer vaapi plugins.I use like this:

rtspsrc rtph265depay h265parse avdec_h265 videosink.And videosink is a gstelement.This code works well.But I want use vaapih265dec to decode.Then I can't get the gpu frame.So,how could i do?

I want to get the gpu frame to mainmemory,such as videosink