Output video does not have Transparent background

[maylortaylor]

I can't get my rendered background video to have a transparent background. In the Remotion UI i see it has my animation and PNG loaded correctly. I see a transparent background in the preview window and the animation runs smoothyl and correctly. However, whenever I render a video, i get a black background instead of a transparent background.

I have tried every combination of render settings but the one that the internet and docs tell me to use are.

// Configure for transparency with ProRes 4444
Config.setPixelFormat('yuva444p10le');
Config.setCodec('prores');
Config.setProResProfile('4444');

I am on a Mac M2 and just using node or the UI to render these. I even tried doing an Image Sequence of transparent PNGs (which worked) but when i used FFMPEG to stich them together, the video has a black background.

[JonnyBurger]

Did you also add Config.setVideoImageFormat("png")?

Does it work with https://www.remotion.dev/templates/overlay instead?
Obviously the software that is playing the video also has to support it. For example in Davinci Resolve you can drag in a video and you will see if it works. Which software did you try to verify that the video has transparency?