DJI packages an HDMI-to-NTSC Composite converter with the Zenmuse. It's small and light weight. Indicates to me that there are chipsets to do this out there at a sane cost, size, and power footprint. All in all meaning, there will be others, ...soon. The quality of such doesn't have to be great as it would only be used to provide a "viewfinder" function via a live video RF back-haul link, of which there are already many pirated from the surveillance video racket. The presentation quality images would be grabbed from the camera's card later for post. I'm guessing it's highly unlikely anyone would attack shipping native HDMI streams via RF, the bandwidth requirments are hurculean. Available frequencies/bands are already at a premium and the modulator linearity requirements aren't easily met, either. Digital coding w/spread spectrum for such ?? Possible, but I'm not holding my breath. NTSC it is, and that's OK.