How to make a gradual download of a video?

Question

HTML

Hello.
If there is a video on the video hosting, you can usually watch it in 3 variations.
1. 360
2. 480
3. 720 The
question is how to store the video on their server in 3 formats and depending on the speed they load the right one. Or they are stored in 720 and they somehow reduce the quality for fast transmission.

Answer 1

The space on hard drives is usually cheaper than the CPU, therefore we store all options, but if the video is not popular, you can store only 720, and get the rest on the fly on request, but this is already optimization. In short, everything depends on the task.