On 2011-07-08 12:32, Mark Callow wrote:
On 08/07/2011 11:54, James Robinson wrote:
True. On OS X, however, the CoreVideo and CoreAudio APIs are specified to
use a unified time base (see
http://developer.apple.com/library/ios/#documentation/QuartzCore/Reference/CVTimeRef/Reference/reference.html)
so if we do end up with APIs saying "play this sound at time X", like Chris
Roger's proposed Web Audio API provides, it'll be really handy if we have a
unified timescale for everyone to refer to.
If you are to have any hope of synchronizing a set of media streams you
need a common timebase. In TV studios it is called house sync. In the
first computers capable of properly synchronizing media streams and in
the OpenML specification it was called UST (Unadjusted System Time).
This is the "monotonic uniformly increasing hardware timestamp" referred
to in the Web Audio API proposal. Plus ça change. Plus ça même. For
synchronization purposes, animation is just another media stream and it
must use the same timebase as audio and video.
Regards
-Mark
Agreed, and the burden of providing monotonic time lies on the OS (and
indirectly the MB, HPET etc. or audio card or GPU clock or whatever the
clock source is.)
So Browsers should only need to convert to/from (if needed) Double and
OS highres time format (which should be there via a OS API in a modern OS).
--
Roger "Rescator" Hågensen.
Freelancer - http://www.EmSai.net/
