Seems to me, all the input(s) are there, to program a simple HUD display in the Video stream. After all the is Linux stuff. Does DJI have open developers?
No they don't even release the changed code when they use open source from other sources!
They offer an SDK if you're into making your own Apps, check at https://developer.dji.com/ and http://forum.dev.dji.com/en
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