[Webkit-unassigned] [Bug 214268] New: iOS 14 Beta - getUserMedia MediaStream ends when attached to two video elements

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=214268

            Bug ID: 214268
           Summary: iOS 14 Beta - getUserMedia MediaStream ends when
                    attached to two video elements
           Product: WebKit
           Version: Other
          Hardware: iPhone / iPad
                OS: Other
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Media
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: tmendoza at twilio.com

In the iOS 14 Beta, video captured with getUserMedia fails when attached to two video elements. 

To reproduce, visit this site:
https://ios14-webkit-video.glitch.me/

When you click on the "Use getUserMedia" button, getUserMedia will be called and the stream will be attached to a <video> element in the DOM. The video will function properly.

When you refresh the page and click on the "Use getUserMedia with dummy element" button, getUserMedia will be called and the stream will be attached to both a <video> element in the DOM and a second <video> element that is not attached to the DOM. This will fail. The video may appear for a moment, but it soon disappears as the underlying MediaStreamTrack ends (see the console to see when the 'ended' event fires).

What is odd is that the video will function properly if the dummy element is appended to the DOM (so that two videos are visible). When the dummy element is not appended to the DOM, the problem occurs.

Source code:
https://glitch.com/edit/#!/ios14-webkit-video?path=script.js


This issue will impact users of the Twilio Video platform (and possibly other WebRTC platforms). The Twilio Video Javascript SDK uses these 'dummy elements' as a way of listening to the 'canplay' event of the <video> element. With this implementation, Twilio users will be unable to capture their local video in iOS 14 as this issue impacts the use of the Twilio.Video.createLocalTracks() function.

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