Why do videos on media players like VLC or some website players suddenly start glitching, making fragments of the video different colors or not refresh parts of the frame at the same time as the rest of them when skipping ahead or back a few seconds?
In: Other
Typically? Compression artifacts.
A video is, essentially, just raw computer code. You can view it as hex or binary and make changes to it using that as well. It’s arranged in a specific way that tells the computer what to display.
Now, you can keep this raw code and it would be mostly fine for a long time. But it would be really big and chances are you want to reduce the size. That’s where compression can come in handy.
Compression works by finding chunks of code that can be “summarized” for lack of a better word.
For example, let’s say you had 10 pixels in a row that are all exactly the same kind of red. You *could* write out the instructions to have red pixels 10 times….or you can say “Do 10 pixels of red”.
Now, compression is far more complex than that and uses a lot of really complicated maths to reduce the image as much as possible without sacrificing the image quality. But it’s not perfect. And each time you run it through a compression algorithm (say reuploading to YouTube) it damages it more and more. Overtime this damage can cause a lot of issues.
Alternatively you can get artifacts from the base code being damaged in someway. Say the video is from a physical medium. When you decide to copy it from that physical medium, the physical device reading it could have dust on it, or there could be a scratch, or the memory using gets hit with a cosmic ray (no, really. It happens…..rarely).
Basically. Something happens between one copy of a video and the next copy that makes the base code change slightly.
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