" 3) How does using a whitelist help?
First, if you don’t use a whitelist, any video that has a resolution of less than 1080p (for example, DVD rips) will be upscaled to 1080p (assuming the Kodi GUI is running at that resolution). If you do use a whitelist then 720p, 576p/i and 480p/i videos can also be output at native resolution. (Section 4 explains why this is desirable)."