Profile: https://share.firefox.dev/3eL7Zw0 This is a profile of playing this 60fps YouTube video in full screen: https://www.youtube.com/watch?v=oakWgLqCwUc I have a 60fps screen, so the only way to play this video without frame skips is to have a composite at every vsync, with every composite presenting a different frame of the video. However, you can see that there are many vsyncs where we "skip" a composite, because [`generateFrame`](https://searchfox.org/mozilla-central/rev/5a4aaccb28665807a6fd49cf48367d47fbb5a19a/gfx/layers/wr/WebRenderBridgeParent.cpp#2035-2036) is false. This causes frame skips. Moreover, these frame skips aren't even counted (bug 1578042).
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In Firefox on macOS, 60fps videos drop multiple frames every second. This causes noticeable stutters. I'm getting around 52 to 56 fps rather than the 60fps that is theoretically possible. Here's a profile: https://share.firefox.dev/3eL7Zw0 It's a profile of playing this 60fps YouTube video in full screen: https://www.youtube.com/watch?v=oakWgLqCwUc I have a 60fps screen, so the only way to play this video without frame skips is to have a composite at every vsync, with every composite presenting a different frame of the video. However, you can see that there are many vsyncs where we "skip" a composite, because [`generateFrame`](https://searchfox.org/mozilla-central/rev/5a4aaccb28665807a6fd49cf48367d47fbb5a19a/gfx/layers/wr/WebRenderBridgeParent.cpp#2035-2036) is false. This causes frame skips. Moreover, these frame skips aren't even counted (bug 1578042).
In Firefox on macOS, 60fps videos drop multiple frames every second. This causes noticeable stutters. I'm getting around 52 to 56 fps rather than the 60fps that are theoretically possible. Here's a profile: https://share.firefox.dev/3eL7Zw0 It's a profile of playing this 60fps YouTube video in full screen: https://www.youtube.com/watch?v=oakWgLqCwUc I have a 60fps screen, so the only way to play this video without frame skips is to have a composite at every vsync, with every composite presenting a different frame of the video. However, you can see that there are many vsyncs where we "skip" a composite, because [`generateFrame`](https://searchfox.org/mozilla-central/rev/5a4aaccb28665807a6fd49cf48367d47fbb5a19a/gfx/layers/wr/WebRenderBridgeParent.cpp#2035-2036) is false. This causes frame skips. Moreover, these frame skips aren't even counted (bug 1578042).