[whatwg] What is the purpose of timeupdate?

Brian Campbell brian.p.campbell at dartmouth.edu
Fri Nov 6 09:11:14 PST 2009

On Nov 5, 2009, at 7:17 PM, Ralph Giles wrote:

> On Thu, Nov 5, 2009 at 6:10 AM, Brian Campbell
> <brian.p.campbell at dartmouth.edu> wrote:
>> As implemented by Safari and Chrome (which is the minimum rate  
>> allowed by
>> the spec), it's not really useful for that purpose, as 4 updates  
>> per second
>> makes any sort of synchronization feel jerky and laggy.
> It really depends what you're doing. It's fine for presentation
> slides, and not too bad for subtitles. I agree it's useless for
> anything moving faster than that.

Our major use case is actually synchronizing bullets, slide changes,  
and the like with video, in educational multimedia produced with high  
production values. I've seen our artists tweak timing of bullets and  
slide changes to within about 1/15th of a second in order to get just  
the right synchronization; our current system has a 1/30th second  
resolution, and I've seen people make changes of 2 frames in order to  
get the synchronization just right.

For captions, or for synchronizing slides when you don't care about  
the precise sync as much, quarter second resolution might be enough,  
but for anything where you need to get the sync to really feel tight,  
it's insufficient.

-- Brian

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