New here and have a question about using chromakey in iMovie. I was testing out a green screen for a future product shoot. I recorded myself waving around a microphone stand, and successfully edited it in iMovie so the background is pure white. It looked great in the iMovie preview until I exported the video, and the background is now a series of strange coloured horizontal blocks and lines.
I am a complete beginner to a lot of this so apologies in advance. May I also ask what the technical name is to those lines and shapes in the background?
I've attached a screenshot of what it look likes in the exported video. For the 'cutaway' in iMovie I used a white .jpg file, but also experimented with .png and .gif but with the same results.
Thanks for any help!