[Webkit-unassigned] [Bug 128731] There is no rate change event when user agent modifies playback rate.

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Fri Feb 14 08:25:33 PST 2014


Eric Carlson <eric.carlson at apple.com> changed:

           What    |Removed                     |Added
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID

--- Comment #11 from Eric Carlson <eric.carlson at apple.com>  2014-02-14 08:22:46 PST ---
(In reply to comment #4)
> The problem is when media player cannot handle playback rate which was set by HTMLMediaElement. In this case UA should update playbackRate in HTMLMediaElement and fire ratechange event.

According to the spec, this is not an issue. You are supposed to do whatever necessary to support an arbitrary rate, eg. pause and buffer data and then play it quickly, pause again, etc. The "playbackRate" attribute should always return whatever value was set [1]:

    The attribute is mutable: on getting it must return the last value it was set to, or 
    1.0 if it hasn't yet been set

This issue was discussed at *great* length on the mailing list a couple of years ago [2], a bug was filed [3], and in the end the working group decided on the current behavior [4][5], eg. when the user agent can't play at the requested rate:

  * playbackRate and defaultPlaybackRate reflect whatever value was set.
  * currentTime changes at a rate as close to playbackRate as possible.

[1] http://www.w3.org/html/wg/drafts/html/master/embedded-content-0.html#dom-media-playbackrate
[2] http://lists.w3.org/Archives/Public/public-html/2011Feb/0113.html
[3] https://www.w3.org/Bugs/Public/show_bug.cgi?id=10837
[4] http://lists.w3.org/Archives/Public/public-html/2011Mar/0682.html
[5] http://lists.w3.org/Archives/Public/public-html/2011Apr/0213.html

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