@plem
The easiest way is to plan ahead and make sure all your media matches up with your output displays to avoid scaling completely. If your display is 1920x1080 with a refresh rate of 30hz, you'll want a camera that captures 1080p @ 30fps, video content that's 1080p @ 30fps, and still images that are 1080p.
Failing that, Isadora scales your content to fit onto your Stage automatically (but scaling means processing power, which is why you want to avoid scaling wherever possible and just make sure that you create or capture media that fits your Stage/Display resolution and refresh rate.
🙂
Best wishes,
Woland