As a multimedia developer, I am wondering about the purpose of the
timeupdate event on media elements. On first glance, it would appear
that this event would be useful for synchronizing animations, bullets,
captions, UI, and the like. The spec specifies a rate of 4 to 66 Hz
for these events. The high end of this (30 or more Hz) is pretty
reasonable for displaying things in sync with the video. The low end,
however, 4 Hz, is far too slow for most types of synchronization;
everything feels laggy at this frequency. From my testing on a two
year old MacBook Pro, Firefox is giving me about 25 timeupdate events
per second, while Safari and Chrome are giving me the bare minimum, of
4 timeupdate events per second.
At 4 timeupdate events per second, it isn't all that useful. I can
replace it with setInterval, at whatever rate I want, query the time,
and get the synchronization I need, but that makes the timeupdate
event seem to be redundant. At 25 timeupdate events per second, it is
reasonably useful, and can be used to synchronize various things to
the video.
So, I'm wondering if there's a purpose for the timeupdate event that
I'm missing. If it is intended for any sort of synchronization with
the video, I think it should be improved to give better guarantees on
the interval between updates, or just dropped from the spec; it's not
useful enough in its current form. To improve it, the maximum interval
between updates could be reduced to about 40 ms, or perhaps the
interval could be made settable so the author could control how often
they want to get the event.
-- Brian
- [whatwg] What is the purpose of timeupdate? Brian Campbell
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