Re: Value of currentTime

We need to be more precise about currentTime updating in blocks, because it
is a bit unclear.  But yes, Joe's answer is the right one (keeping in mind
you should be sure to be scheduling ahead a bit, as this example does).


On Tue, May 27, 2014 at 8:29 AM, Arnau Julia <Arnau.Julia@ircam.fr> wrote:

> Hi Joseph,
>
> Thanks for your answer. I really know how to start two sources at specific
> time. It is more that I would like to know how it works because I didn't
> find nothing about that in the specification. :-)
>
> Thank you,
>
> Arnau
>
> On 27 mai 2014, at 17:17, Joseph Berkovitz <joe@noteflight.com> wrote:
>
> Hi Julia,
>
> Setting aside the part of your post that relates to the rate at which
> currentTime is updated, I wanted to note that it is easy to start two
> sources at a specific time:
>
> On May 27, 2014, at 10:06 AM, Arnau Julia <Arnau.Julia@ircam.fr> wrote:
>
> Therefore, as I understand, if I want to start two sources at a specific
> time I can't do something like this,
>
> function start(){
> source1.start(audioContext.currentTime+1);
> source2.start(audioContext.currentTime+1);
> }
>
> because it's not possible to guarantee that the currentTime for these two
> instructions will be the same.
>
>
>
> You could, however, do this, if you wanted to be completely sure:
>
> function start(){
> var t = audioContext.currentTime+1;
> source1.start(t);
> source2.start(t);
> }
>
> Overall I don’t think it is a good idea (even if it were possible) to rely
> on sample-accurate ("a-rate") updates of the currentTime clock in the main
> thread, because there is always some unpredictability in the thread’s
> timing, and it’s likely to be large relative to the duration of a sample
> frame. The main browser thread can yield CPU time to other interrupt-driven
> processes (including things outside the browser) at some point between
> acquiring currentTime’s value and employing that value for scheduling
> purposes.
>
> .            .       .    .  . ...Joe
>
> *Joe Berkovitz*
> President
>
> *Noteflight LLC*
> Boston, Mass.
> phone: +1 978 314 6271
> www.noteflight.com
> "Your music, everywhere"
>
>
>