Background picture Size for an 360° Project

Hey there everyone,

I am using Captivate2019.

i started a new 360° Project for 1024x768. But when i set a new background picture its always very low quality.

I took anything from 1920x1080 to 1024x768, every picture just got scaled downwards and looks extremly pixelated.

So know for my question: which size is required for the 360° background picture, for my project size? Because i sadly didnt find any information in the internet about that topic.

Thanks in advance for your help.