Why does YouTube videos with lots of greenery or trees cause lag?
In: Technology
There are a few tricks you can do to make video easier to stream – different ways of compressing video. One way is to only save changes to the pixels. Turn this pixel green, and then until you get new instructions, it stays that color green. Instead of sending data for that pixel for every frame, you only have to send the data for the new color when it changes.
You can also use data about surrounding pixels. It loses quality, but you can save every other pixel and then average them. If one pixel is this shade of green, and the pixel one over is a slightly different shade of green, then the pixel between them is *probably* a shade of green between the two.
Lots of foliage in a video breaks both of those techniques. There are a *lot* of very subtle but different colors that change a lot with even a little bit of wind or movement. There’s a lot of detail that needs to be preserved, so pixels can’t be averaged and because they change often, you have to send data with every frame. Other methods of compression fail similarly.
The bandwidth from the server is designed for compressed video. When the compression doesn’t work anymore, there isn’t enough bandwidth to keep up with the demand, and the video lags or the quality drops. Tom Scott has an [excellent video](https://www.youtube.com/watch?v=r6Rp-uo6HmI) about bitrate and how different things can negatively impact it.
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