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[Bug 12227] New: The readyState check in the "potentially playing" definition should not be used to influence GC of media elements

From: <bugzilla@jessica.w3.org>
Date: Wed, 02 Mar 2011 23:49:48 +0000
To: public-html@w3.org
Message-ID: <bug-12227-2495@http.www.w3.org/Bugs/Public/>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=12227

           Summary: The readyState check in the "potentially playing"
                    definition should not be used to influence GC of media
                    elements
           Product: HTML WG
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P3
         Component: HTML5 spec (editor: Ian Hickson)
        AssignedTo: ian@hixie.ch
        ReportedBy: adrianba@microsoft.com
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-wg-issue-tracking@w3.org,
                    public-html@w3.org


See the thread starting at [1] including [2] and [3].

We've analysed this section of the spec.
http://dev.w3.org/html5/spec/video.html#media-playback

This uses the phrase "potentially playing", which is defined as:

"A media element is said to be potentially playing when its paused
 attribute is false, the readyState attribute is either HAVE_FUTURE_DATA
 or HAVE_ENOUGH_DATA, the element has not ended playback, playback has
 not stopped due to errors, and the element has not paused for user
 interaction."
http://dev.w3.org/html5/spec/video.html#potentially-playing

The problem with this is that there is still a race between the GC and the
network in this example:

function playAudio() {
  var a = new Audio("http://www.example.com/music");
  a.play();
}

This means that after the function exits, the behaviour will vary depending
upon whether the GC fires before or after readyState gets to HAVE_FUTURE_DATA.

We propose removing the readyState check from potentially playing this specific
scenario so that the element will only be available to be collected on error,
when paused, at the end of the media, or if somehow stopped by user
interaction.


[1] http://lists.w3.org/Archives/Public/public-html/2011Jan/0438.html
[2] http://lists.w3.org/Archives/Public/public-html/2011Feb/0006.html
[3] http://lists.w3.org/Archives/Public/public-html/2011Feb/0007.html

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Received on Wednesday, 2 March 2011 23:49:50 UTC

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