A tale of 2 videos

Hi, can you me help please? (maybe I am just stupid - tell me if I am)

Problem compositing 2 videos. Videos are each a clip of PRN files. The second clip is the overlay with alpha transparency for the most part. In theory, I thought the following would work but it doesn’t. Tried usual settings like Fac. The alpha appears as solid black and obscures Clip 1. It works if I swap Movie Clip 2 with ‘Render Layers’ but it only works as a still image. AAAAAAAAACH!!!

Movie Clip 1
Movie Clip 2 (with alpha)
||
Alpha Over
||
Composite

Well you’ve stumped me. What is a PRN file? Perhaps you can transcode to a blender friendly format instead?

There are several fixes to this. But I think the problem is that PRN is not a common video format. (As far as I just understood it’s based on vectors.) Most common video formats don’t support alpha channels anyways, sequences with alpha are best used with an image sequence.

If there is actual black (000000) where your alpha is supposed to be, you can just create the alpha channel using a maths “greater than” node.