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Re: Time coordinates and audio-visual synchronization ... again

From: Srikumar K. S. <srikumarks@gmail.com>
Date: Fri, 4 Jul 2014 07:41:55 +0530
Cc: Joseph Berkovitz <joe@noteflight.com>, Audio WG <public-audio@w3.org>
Message-Id: <2DA6C216-B462-44BA-B16E-C95A7262FF08@gmail.com>
To: Chris Wilson <cwilso@google.com>
Chris and Joe - That is correct indeed. I’m including the relevant quotes here for reference -

"Since the time values of the document timeline are relative to the navigationStart time,document.timeline.currentTime will roughly correspond to Performance.now() [HR-TIME] with the exception that document.timeline.currentTime does not change within a script execution block as defined in section 5.25 Script execution and live updates to the model.”

In 5-25, there is an explicit guarantee made that the time passed to a requestAnimationFrame callback is exactly the same as document.timeline.currentTime.

Best,
-Kumar


> On 3 Jul 2014, at 9:35 pm, Chris Wilson <cwilso@google.com> wrote:
> 
> I agree with Joe - Performance.now() is the standard for system time.
> 
> 
> On Thu, Jul 3, 2014 at 8:53 AM, Joseph Berkovitz <joe@noteflight.com> wrote:
> Hi Kumar,
> 
> My read on this is since the Web Animations draft appears to correlate animation timelines to Performance.now(), this issue would be resolved by whatever action Web Audio takes to address the current difficulties in relating audio context time to Performance.now().  That issue is captured in:
> 
> 	https://github.com/WebAudio/web-audio-api/issues/340
> 
> Best,
> …Joe
> 
> On Jul 2, 2014, at 2:16 PM, Srikumar K. S. <srikumarks@gmail.com> wrote:
> 
>> I just came across a Google I/O talk about a proposed draft of a “Web Animations 1.0” 
>> API which already comes with a polyfill for all major browsers.
>> 
>> http://dev.w3.org/fxtf/web-animations/
>> 
>> How should developers go about coordinating sound precisely in relation 
>> to animations as declared using this API?
>> 
>> Best,
>> -Kumar
> 
> 
> 
> .            .       .    .  . ...Joe
> 
> Joe Berkovitz
> President
> 
> Noteflight LLC
> Boston, Mass. phone: +1 978 314 6271
> www.noteflight.com
> "Your music, everywhere"
> 
> 




Received on Friday, 4 July 2014 02:12:29 UTC

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