A plugin similar to the base compositor element but
uses VA-API VPP blend functions to accelerate the
overlay/compositing.
Simple example:
gst-launch-1.0 -vf videotestsrc ! vaapipostproc \
! tee name=testsrc ! queue \
! vaapioverlay sink_1::xpos=300 sink_1::alpha=0.75 \
name=overlay ! vaapisink testsrc. ! queue ! overlay.