system
Given the following post, respond as if you're commenting on Reddit:
human
How come when pixels on an HD TV "glitch," they follow things like people?
gpt
It's due to the way video compression works. Raw video would need extremely huge bandwidth (bits it takes to encode a second of video), so data compression techniques are used to lower the bandwidth usage to be able to fit on a DVD or being streamed over the internet. Using current compression techniques we are able to achieve huge reductions in file size as we can cram a full HD image in 6mbps (megabit/second) and still retain decent quality. Uncompressed HD footage can go up to 190mbps.

To achieve this, video frames a grouped together and encoded. Simply put, the differences between each frame are described rather as encoding each frame as a separate entity. So when a TV 'glitch' you see only the 'changes' between frames (often moving objects) until the video hits its next keyframe (every now and then a complete frame is embedded) and the decoder can start fresh from a complete image.

These glitches can happen because decoders are build to handle missing data or malformed data which inevitably will happen when reading media from the internet or optical storage.