Why do khanacademy videos load comparatively much faster?

So, I have noticed that khanacademy videos load much faster. The reason I have come to know from the following discussion is the predominant use of black in videos. So it can be compressed much more.

Q: In countries like mine we don't have many people who can afford high broadband speeds.It takes a lot of time for any kind of videos to buffer.But KHAN ACADEMY videos,they load in a flash!

A: I know the question (and the answer) is off topic but it makes a change for me to be able to answer something: It's because there is a predominance of one colour - black - and so the video can be compressed by the sender's system to a much greater extent. On a typical row of the video, instead of sending 800 black pixels and 1 green pixels - for example), the sender sends something like "0*800" and "256*1" and the receiver interprets that at the other end (I just put in 0 and 256 because those are the RGB codes for black and green).

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