I've always noticed that whenever I'm watching a youtube video or twitch stream where for whatever reason the screen goes to static (usually in a video game) all other things in the video on top of it become very blurry as if the video has a very low bitrate. However as soon as the static stops the quality goes back up. Why is this?
Posted Dec 31, 2018, 11:22 PM UTC
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All that information about the video static has to be transmitted, so you've greatly increased the amount of information that needs to be sent. This is made worse by the compression algorithms used, since "random" noise is very difficult to compress much. In fact, the worst signal for bandwidth requirements is one of completely random noise.
Online video is compressed. The primary method of video compression is to look for patterns and remove them and replace them with a reference to that pattern. So, a large block of a single color like the sky could be replaced by a single reference to the color blue which saves tons of space.
Static has no pattern because it's almost completely random. There's no way to predict what will come next so it's really hard to compress it. They still do compress the video because they have to but they do it in a way that looks way worse. The compression is much more noticeable than if there was a simple pattern on screen.
Here's a great video from Tom Scott on the topic: https://www.youtube.com/watch?v=r6Rp-uo6HmI
Random noise does not compress at all. Video transmission relies on heavily reducing the amount of data transmitted by compression. If you have black screen with a red circle going from one end to another, I already told you what the screen is like, in just a couple of words. But white noise? Describing screen takes exactly pixel count of screen * data needed to describe individual pixel. That's a worst case scenario possible.
So what happens is, software is configured to throw data out until it fits some maximum bitrate allowed(because video requiring gigabytes of data transmitted every second would just not work). And it does this fairly, white noise gets blurred, and everything else gets blurred. So the larger the white noise section on screen, the more it requires whole image to be simplified for it to fit through set bitrate limits.
Imagine the video is of a plain blue screen with say a red ball moving across it , the data sent doesn't need to change to much except to change the next lot of pixels around the ball, now if it's say black and white static, all the little black and white specks need to be updated each data packet, also why Say at the end of the Superbowl when they release all the confetti it makes the picture look crap.