[Webkit-unassigned] [Bug 273103] New: HTMLVideoElement "playing" event triggered unexpectedly

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=273103

            Bug ID: 273103
           Summary: HTMLVideoElement "playing" event triggered
                    unexpectedly
           Product: WebKit
           Version: Safari 17
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Media
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: ethanchong at canva.com

Issue: "playing" event is emitted unexpectedly

Description: 
We observed that the "playing" event triggers before the video player is potentially playing (https://html.spec.whatwg.org/multipage/media.html#event-media-playing) on Safari browsers. This is obvious when the internet is slow and the video content takes a while to be downloaded. 

Observations:
1. Unlike other browsers, Safari does not resume video playback once the video player has downloaded enough data for both the current and future frames, denoted by a readyState of 3 and the emission of a 'canplay' event.
2. "playing" event triggers after the "canplay" event is emitted.
3. The video player only resumes playback once it estimates that users can play the video without any pauses. This is denoted by a readyState of 4, which corresponds to the emission of a 'canplaythrough' event.

Reproducible on Desktop Safari and IOS Safari with simple HTMLVideoElement and console logging the media events. (See the attached index.html)

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