As also written in this TX2 thread chroma keying does not work.
Via chroma keying, e.g. blue can be set as the fully transparent colour and should work with this code:
gst-launch-1.0 \ videotestsrc pattern=snow ! video/x-raw, framerate=10/1, width=1920, height=1080 ! \ alpha alpha=1 ! nvvidconv ! mix.sink_0 \ \ videotestsrc pattern=smpte75 ! video/x-raw, framerate=10/1, width=700, height=700 ! \ <b> alpha method=blue</b> ! nvvidconv ! mix.sink_1 \ \ nvcompositor name=mix sink_1::xpos=500 sink_1::ypos=100 \ sink_1::width=600 sink_1::height=600 sink_1::alpha=0.5 sink_0::alpha=1 ! nv3dsink \
However, Jetson nano gives me an image with a black region instead of snow pattern, see screenshots. Transparency works fine, but that is not chroma keying. Finally, only the black (former green/blue) bar must be fully transparent.
Similar images where shown from rary in post #3 and #5. Rary wrote in #1 in his thread that his code works fine on another Linux machine.
I checked a lot of possibilities:
both alpha alpha=0…1
nvvidconv ! nvegltransform ! nveglglessink
In my opinion it is a bug. So it would be very nice if someone would inform the developers.
I’ m using jetson nano with jetson-nano-sd-r32.2.1.zip
Thank you for your support.