So you got me curious...It's tedious, but it can be done in a creative work around.....


It involves using either two outputs, or an output and a mix bus.

Make a video starting in a solid color that will work for your show as a luma/chroma key that then transitions to Alpha using your custom transition.
The solid color you Key will be where program lives, and the alpha reveals preview.

Bring your video in as an input (lets call this input 1)

Assign an output to preview, and then create an NDI input of same output (lets call this input 2). In this input assign the video(input 1) to the multi-overlay. It will cover "preview" and reveal it as the alpha transitions in the video.

You now need an input that is the rendered version of input 2 (because you can only key on the main layer). You can either do this with an output and NDI input the same we did to pull preview in, or a mix input. (Lets call this input 3). Do the appropriate chroma/luma key to remove the solid color of the video on input 3. Where it gets tricky, is your key will have an effect on what is being revealed, so it needs to be something that won't key out your content during the transition as well....If you don't understand, start playing with it and you'll see what I mean.

The result is Input 3 ends up with an alpha channel that transitions to preview via what was originally alpha channel in input 1. Input 2 replaces the original alpha channel with preview. You can then use input 3 as the input for a stinger. Set the cut point for the length of your original video (input 1). I also ended up putting triggers on Input 3. One that plays Input 1 on overlayIn as well as one that restarts input 1 after a small delay on OverlayOut.

Probably not realistic to do on most shows, but was a fun experiment none the less.