[Webkit-unassigned] [Bug 221334] New: Audio passed through WebAudio is delayed and glitchy on Safari

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=221334

            Bug ID: 221334
           Summary: Audio passed through WebAudio is delayed and glitchy
                    on Safari
           Product: WebKit
           Version: Safari 14
          Hardware: All
                OS: All
            Status: NEW
          Severity: Blocker
          Priority: P2
         Component: Web Audio
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: jjv360 at me.com
                CC: cdumez at apple.com

Hi, currently in all latest versions of Safari (Mac and iOS) there are audio issues when passing audio through WebAudio. Here's a codepen showing the issue: https://codepen.io/jjv360/full/dyOYXvE

On Mac the problem is only to do with delayed audio (the iOS issue below does happen, but much more rarely). You can run the audio sync test in the codepen and see that it almost always has around a 1 second delay. This does not happen in Chrome or Firefox.

On iOS the problem is far worse (this does happen on Mac too, but not nearly as often) and has caused us to warn our users to not use Safari for now. On iOS, the audio sometimes stutters and has tiny gaps of silence (about 1 in 4 times of refreshing the page), which widen the longer the video is played. Eventually, there is no audio at all and it's completely silent. Oddly enough, killing the browser results in about a 1 second of that silent audio playing, almost as if a buffer is full and it just got flushed. This is most noticeable on the iPhone 7, though it happens on all iOS devices. The best way to reproduce it, is if you connect bluetooth headphones, play the video in the codepen above, and then press Access Microphone, this seems to almost always trigger the bug.

This has been tested and reproduced on:
- Safari on iOS 14.4 on an iPhone 7
- Safari on iOS 14.4 on an iPad Pro 4th gen
- Safari on macOS 11.2 on a MacBook Pro 15" 2017

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