Talking about it, in PowerPoint when you import a movie or an animated GIF it shows in 'true' resolution while editing (i.e. a 'file' pixel takes a 'screen' pixel) and when going to 'full screen'/'presentation' mode it scales it up (i.e. resamples the image with some sort of undocumented dithering technique), which most of the time goes unnoticed but in fact makes the image quality a bit worse.