<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
