Hi,
You may utilize nvcompositor. Please refer to
$ gst-launch-1.0 videotestsrc ! video/x-raw,format=UYVY,width=1920,height=1080 ! nvvidconv ! 'video/x-raw(memory:NVMM),format=RGBA' ! comp.sink_0 videotestsrc ! video/x-raw,format=UYVY ! nvvidconv ! 'video/x-raw(memory:NVMM),format=RGBA' ! comp.sink_1 nvcompositor name=comp sink_1::xpos=10 sink_1::ypos=10 sink_2::xpos=50 sink_2::ypos=50 ! nvoverlaysink