Implement "Image Filter" protocol for movies and "Filtered Movie" export option.
Would pass the audio track through unchanged.
For the Community Edition, the same 1280x1280 image-size restriction as the current movie export feature would apply.
SyphonCast is an app created in Vuo 2.0.2, it looks at the primary and secondary displays connected to your Mac and allows the user to choose which display they would like to screen mirror over to Syphon. SyphonCast appropriately scales the resulting image to the broadcast resolution chosen. By default the settings are Primary Display at 1080p resolution.
I created this app to use with NDISyphon to allow me to broadcast my displays over the network to another computer.