Re: Purpose and synchronicity of timeupdate events across devices?

Hi Francois

Excellent work with the timing object ! Here's a quick reply on the
timeupdate event.

The timeupdate event was never intended to be in sync across devices. Of
course, one could support this, but I'm in favour of doing this as a
separate thing, for instance by providing new versions of setTimeout or
setInterval - as indicated in the task description. (possibly we need new
names here to avoid confusion)

Personally, I'm no huge fan of the timeupdate event (with fixed frequency).
In my opinion, the choice of frequency should be in the consumer of the
timingobject - for instance allowing different components to sample the
timing object at very different rates.
The timeupdate event was only introduced in the spec to mimic the
pulse-based timing model of the HTMLMediaElement (which is about 5Hz),
which programmers are used to in the Web environment. Ironically, a central
motivation for the timing object is to escape this pulse-based timing
model, so in that regard the timeupdate event may even be
counter-productive.

So, if you want to remote it - I would be ok with that :)

Ingar



2015-06-08 17:35 GMT+02:00 Francois Daoust <fd@w3.org>:

> Continuing to think out loud here,
>
> What is the purpose of the "timeupdate" events as currently defined?
>  http://webtiming.github.io/timingobject/#events
>
> More specifically:
>
> 1. Is the expectation that "timeupdate" events get fired synchronously
> across devices, or that they are associated with the "position" of the
> timing object? The spec does not suggest that and I did not do that in my
> prototype implementation, but then it seems a bit useless if it is only a
> shorthand to the local setInterval function.
> 2. Why a 5hz fixed frequency? Is it a common frequency for most
> media-related operations? Not having any sort of flexibility seems weird.
>
> I guess I see value in having something synchronized across devices and a
> bit more flexible, synchronized versions of "setTimeout" and "setInterval"
> in short that could be exposed on a TimingObject instance. I see that it is
> in fourth position in the list of tasks for the group, so that's good ;)
>   https://www.w3.org/community/webtiming/overview/
>
> Francois.
>
>