Create a 5 second preview for a video file. How?

Question

PHP

On YouTube or many other video hosting sites, I often saw such a feature that when you hover the mouse over the preview of the video, a 5-second fragment from the video itself is played (somewhere around the middle).
The question is how and by what means is this done?
ZY - I see the easiest way to assemble a GIF file using avconv on the server. Next, on the hover event, play this GIF instead of the static preview.
But an inner voice says that this is not the right way. where to look, where to dig? Thanks for the replies in advance.

Answer 1

The same youtube returns webp animation (consider gif)
The question is whether rendering is in real time / cache or prepared in advance.

Answer 2

Prepare a preview with ffmpeg, in the same webp, then save it to disk and change the static preview to a preview in webp about hover.

Answer 3

Switched from gif format to webp