This seems more like a bug than a feature request, but we need to be able to cleanly transition between sources that have alpha channels. Currently (to steal from ERZY's post):

"The problem becomes visible every time when I try to fade into a source with transparency (PNG files, vMix titles etc.). The former content is not faded out in alpha channel, but is cut hard on the transition end. It applies to fade and merge transitions. It works perfectry the other way round - fading from content with transparency into something with no transparency."

For our use case, we typically use vMix for graphics and video playback. When cueing up a series of PNG's for credits, for example, the images cannot properly "dissolve" between each other. The same is true if trying to use a title, or even a powerpoint with a luma or color key. They pop in and out rather than dissolving.

See this forum topic for more info:
https://forums.vmix.com/...Aplha-transition-problem