[gow] (2) Specify how frequently the timeupdate event should fire.

git-svn-id: http://svn.whatwg.org/webapps@2407 340c8d12-0b0e-0410-8428-c7bf67bfef74

index

    steps.</li>
 
    <li><p>If the time was reached through the usual monotonic increase
-   of the current playback position during normal playback, the user
-   agent must then <a href=#queue-a-task>queue a task</a> to <a href=#fire-a-simple-event>fire a simple
-   event</a> called <code title=event-timeupdate><a href=#event-timeupdate>timeupdate</a></code> at the element. (In the
+   of the current playback position during normal playback, and if the
+   user agent has not fired a <code title=event-timeupdate><a href=#event-timeupdate>timeupdate</a></code> event at the element in
+   the past 15 to 250ms, the user agent must then <a href=#queue-a-task>queue a
+   task</a> to <a href=#fire-a-simple-event>fire a simple event</a> called <code title=event-timeupdate><a href=#event-timeupdate>timeupdate</a></code> at the element. (In the
    other cases, such as explicit seeks, relevant events get fired as
    part of the overall process of changing the current playback
-   position.)</li>
+   position.)</p>
+
+   <p class=note>The event thus is not to be fired faster than about
+   66Hz or slower than 4Hz. User agents are encouraged to vary the
+   frequency of the event based on the system load and the average
+   cost of processing the event each time, so that the UI updates are
+   not any more frequent than the user agent can comfortably handle
+   while decoding the video.</li>
 
    <li><p>If the time was reached through the usual monotonic increase
    of the current playback position during normal playback, and there

source

    steps.</p></li>
 
    <li><p>If the time was reached through the usual monotonic increase
-   of the current playback position during normal playback, the user
-   agent must then <span>queue a task</span> to <span>fire a simple
-   event</span> called <code
+   of the current playback position during normal playback, and if the
+   user agent has not fired a <code
+   title="event-timeupdate">timeupdate</code> event at the element in
+   the past 15 to 250ms, the user agent must then <span>queue a
+   task</span> to <span>fire a simple event</span> called <code
    title="event-timeupdate">timeupdate</code> at the element. (In the
    other cases, such as explicit seeks, relevant events get fired as
    part of the overall process of changing the current playback
-   position.)</p></li>
+   position.)</p>
+
+   <p class="note">The event thus is not to be fired faster than about
+   66Hz or slower than 4Hz. User agents are encouraged to vary the
+   frequency of the event based on the system load and the average
+   cost of processing the event each time, so that the UI updates are
+   not any more frequent than the user agent can comfortably handle
+   while decoding the video.</p></li>
 
    <li><p>If the time was reached through the usual monotonic increase
    of the current playback position during normal playback, and there