Make media.currentTime more accurate during seeking #7638
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Previously, currentTime always returned the "official playback position", which is only periodically synced with the "current playback position". In particular, if JavaScript code performs a seek (e.g. using the seek() method), this would not sync them until a stable state is reached. (I.e., until that JavaScript code runs to completion.) This shows up particularly in the case where currentTime is set to a value outside of the timeline, e.g. Number.MAX_VALUE. The previous spec would cause whatever is passed to the currentTime setter, to then be returned by the currentTime getter. But Chromium and Gecko instead clamped the result to the timeline. Chromium's implementation of this, in particular, is to return the current playback position during the seek process, which is what we have specified here. See web-platform-tests/wpt#32832 for more discussion.
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If I understand the changes proposed by @domenic correctly, setting So, you'd end up with something like: And this ends up with weird behavior if you do something like: Where video1 will get seeded to video2's initial currentTime, not 120, and not 120 clamped to video2's duration. Am I misunderstanding the proposal to return |
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Even if the above issue is fixed (for example, by modifying the "current time setter steps" to clamp "given value" to the media timeline), this still leads to weird behavior where, e.g.: Will result in video1's |
Previously, currentTime always returned the "official playback position", which is only periodically synced with the "current playback position". In particular, if JavaScript code performs a seek (e.g. using the seek() method), this would not sync them until a stable state is reached. (I.e., until that JavaScript code runs to completion.)
This shows up particularly in the case where currentTime is set to a value outside of the timeline, e.g. Number.MAX_VALUE. The previous spec would cause whatever is passed to the currentTime setter, to then be returned by the currentTime getter. But Chromium and Gecko instead clamped the result to the timeline. Chromium's implementation of this, in particular, is to return the current playback position during the seek process, which is what we have specified here.
See web-platform-tests/wpt#32832 for more discussion.
(See WHATWG Working Mode: Changes for more details.)
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