How does AMP determine the time to load the video when using amp-video in amp-story?

Question

The element loads the video resource specified by the src attribute lazily, at a time determined by AMP.

How does the AMP determine the time to load?

This is an internal implementation detail of AMP and not something that publishers should rely on, as it can be changed at any time. Is there a specific reason why you would need to know this? — Jon Newmuis
Is your question why I would want to know the time to load for AMP pages? — MobiCycle Ltd
Rather: amp-story will load videos before they are shown on screen, but the exact timing can depend on a number of different factors. As a publisher of amp-story documents (or AMP documents generally), this is not something you control directly, nor should you need to worry about. — Jon Newmuis
Are you saying to the owner of a website that they should not "worry about" how long it takes for videos on their webpage to load? — MobiCycle Ltd
Sorry -- there's the matter of how long the videos will take to load and, separately, the matter of when the video loading will be initiated. AMP doesn't have much to do with how long the video will take to load, but does do a lot of optimization around when the video should begin to load. For amp-story specifically, I recently gave a talk on some of the factors that we currently take into account for determining when videos should begin to load, but there are indeed other factors and they will all likely change over time. — Jon Newmuis

Jon Newmuis Jon Newmuis · Accepted Answer · 2018-10-15T16:18:26

A rough outline of the video loading strategy used within amp-story can be found in AMP story's Media Pool documentation. Additionally, there is a talk on YouTube that describes this as well.