Science behind the longest night’s (game of thrones) poor quality

Last night’s episode of “Game of Thrones” was a wild ride and inarguably one of an epic show’s more epic moments — if you could see it through the dark and the blotchy video. Images on video can be incredibly detailed, but places where there are subtle changes in color — often a clear sky or some other large but mild gradient — will render in large stripes as the codec goes from “darkest dark blue” to “darker dark blue” to “dark blue,” with no “medium darker dark blue” in between. This kept the brightness of the background just high enough that the codec had to represent it with one of its handful of dark greys, and the subtle movements of fog and smoke came out as blotchy messes (often called “compression artifacts” as well) as the compression desperately tried to pick what shade was best for a group of pixels.

Source: techcrunch.com