Question / Help Use b\w or alpha video (not image) to combine two another videos


New Member
I know you can use image as mask. But I would like to use animation as mask. And I don't know how to set this up with current tool set. Do I miss something?
I have this video, I can have it b\w or white + alpha

I want so black was mediaA and white was mediaB


Like here but animated mask


New Member
I'm also extremely interested a response to this. I have a similar application - not an animated mask like that, but dynamically coming in from an NDI source. I'd love to be able to set a video source as the Image Mask/Blend filter source.


New Member
Thanks, I'll take a look at this later this evening and see if I can make it work. I'm using StreamFX already for the Blur effect, and it seems like I've tried the Dynamic Mask, but I don't remember off hand what problems I was having with it. User error most likely. I'll give it another go.


Active Member
I haven't used it myself, but it may require adding your mask element as a source within the scene, and pointing the Dynamic Mask to use that source.


New Member
I've messed around with it a little, and I can kind of get it to do what I want. I'm able to get it to dynamically pick up the mask coming from a live NDI source. I can even manage some edge alpha-blending. I'll have to keep tweaking it, but this has some promise.

What I really want probably isn't possible with any system using only two inputs (main cam and an overlay with a mask). I'm trying to put text over a video in various locations coming from a second presentation machine (hence the dynamic mask). If I stick with simple chroma-keying and block edges, this is easy. But I really want a blurred section of my video under the text, with the edges of the blur blended back into the sharp video. So really, I'm trying to figure out how to do a 3-4 layer application with only two source layers.

The presentation layer order is effectively (from top to bottom of the stack):
  1. Presentation Text
  2. Blurred Camera
    1. Apply mask/key (from presentation machine) with blended alpha edges
  3. Camera
But I only have two sources: Camera and the Presentation NDI feed. The Dynamic Mask filter works for the blended alpha edge, but also takes out part or all of my text as well. I'd have to have two coordinated layers from the presentation machine (text and mask separately) to make it work right, I think. I'll probably end up not worrying about the blended alpha edges and just stick with a chroma-key for my mask. Thanks for the tip about trying the Dynamic Mask though!