[Webkit-unassigned] [Bug 216250] New: Major WebGL video texture performance regression in iOS 14 beta

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=216250

            Bug ID: 216250
           Summary: Major WebGL video texture performance regression in
                    iOS 14 beta
           Product: WebKit
           Version: Other
          Hardware: iPhone / iPad
                OS: Other
            Status: NEW
          Severity: Major
          Priority: P2
         Component: WebGL
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: simontaylor1 at ntlworld.com
                CC: dino at apple.com

Based on the current iOS 14 beta (beta 7) the performance of texImage2d from a video element has suffered a significant regression since iOS 13.

Some examples pages that have the very simplest shader and render loop for getting a 720p video into a WebGL canvas:
https://tango-bravo.net/WebGLVideoPerformance/texImage2d_video.html (uses gl.RGB format and internal format)
https://tango-bravo.net/WebGLVideoPerformance/texImage2d_video_rgba.html (uses gl.RGBA format and internal format)

On an iPod 7th gen running iOS 13.6, I've observed the reported total average draw time under 2ms for both of these and it has no difficulty maintaining a 60FPS render loop (aside: iOS seems to downclock when hitting 60FPS; opening the app switcher and interacting with the page (scrolling, zooming, etc) looks to bring the timings down).

With an iPhone XR on the iOS 14 beta 7, things are significantly worse. With the first example the render loop drops under 60 FPS (and the bulk of the time seems to be spent in drawElements). With the RGBA format (second link) 60 FPS is maintained but the timings remain high (above 7ms).

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