Hi,
Please try Honey Patouceul’s suggestion. And please share your release version( $ head -1 /etc/nv_tegra_release )
The property background-w and background-h should work only on r32.4.x + this patch:
Gstreamer using nvcomposer to filesink hangs, but nvcomposer to nvoverlaysink works fine - #19 by DaneLLL