Fix video decode running before start time #4751
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| var nextFrame = availableFrames.Count > 0 ? availableFrames.Peek() : null; | ||
| // if not looping and not yet having reached the start of the video, don't attempt to consume frames yet. | ||
| // if we begin consuming frames the decoder will be performing unnecessary work. | ||
| if (!Loop && PlaybackPosition < 0) |
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I assume the loop exception here is to make sure that even with negative time the video can loop. Which would be fine, aside from the fact that as far as I can see, looping in negative time is completely busted right now.
With this branch as-is, when I run the TestDecodingContinuesBeforeStartTimeIfLooping I get a bunch of Video too far out of sync log messages. Which is because of this code in AnimationClockComposite:
The % is, unfortunately, not the nice math modulo (which guarantees that the result is in the interval [0, $right_operand]). It can be a signed value. In particular, e.g. -1000 % 600 = -400. Which cannot be seeked to as there are physically no frames with that time.
But even with that fixed the animation doesn't play properly for reasons that I'm not entirely sure of yet (still spews Video too far out of sync, albeit at a lesser rate). But, the bigger point is, if PlaybackPosition was properly fixed to never return anything outside of the [0, $duration] range, this guard wouldn't be needed anymore, I don't think?
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weird, that didn't happen when i tested.
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Actually based on how things are written, I don't think looping before zero time is even correct. I'll update the logic to align with this expectation.
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I've updated PlaybackPosition to be clamped as proposed. Seems to work well, and avoid the negative effect of the early return (potentially not buffering the initial frames of the video as early as possible).
…running-before-start-time
Noticed that we were continuously decoding frames before a video started due to no checks in place.
Note that I did some code quality improvements around the
outOfSynclogic but the only part which matters is the early return.