[SOLVED] Transparent PNG Rendering Question

Hi. New to these forums, but not to Shotcut. Just curious about why a transparent PNG file needs to have a background of some kind behind it to show things such as anti-aliasing. If I drop a PNG with nothing behind it, the text is all pixelated and things like semi-transparent images just look like monochromatic blobs. If I render the PNG with a color background, it looks fine. If I add a color background track in Shotcut below a transparent PNG it looks fine. Same with placing a transparent PNG over a video. I noticed this behavior isn’t in Kdenlive and a couple other video editors, but a goodly number show these transparent PNG’s like Shotcut. I’m curious. The default background to the video tracks is already black. Why won’t the PNG’s show properly? I did a quick video today to show what I mean if my explanation here isn’t clear. https://youtu.be/Q13wn41IaYI I don’t know if this is a feature or a bug. It’s not just limited to Shotcut, so I’m guessing it has to do with how the timelines are setup? It’s not keeping me from using Shotcut. TIA for any help in understanding.

It is a performance optimization. In order to render that with anti aliasing it would have to blend everything on the lowest video track with the hidden black background track. But that is wasteful when most people use opaque video on the lowest video track. It is not a big deal on the other hand to add a video track on the bottom with a long color clip for your special needs.

Terrific! I understand, now. Thanks for explaining it. You’re absolutely right; it’s not a big deal to put in a background. I was curious as to why. Thanks again.

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