An incomplete quote from the policy statement is below. I strongly encourage y'all to read the entire article, since there's more conditions than I'm pasting here, but these are the highlights that answer your question.

https://webkit.org/blog/6784/new-video-policies-for-ios/

"<video> elements will be allowed to autoplay without a user gesture if their source media contains no audio tracks."

"<video muted> elements will also be allowed to autoplay without a user gesture."

"If a <video> element gains an audio track or becomes un-muted without a user gesture, playback will pause."