The Patch Time patch outputs whatever time it was asked to render at.
If you are using a QCView (as the editor is) then the timing is
essentially an implementation detail and you should not rely on any
false behavior, in fact if you are noticing drift that affects your
work you should write a bug at bugreporter.apple.com. I myself have
not been able to reproduce this in the editor so make sure you include
a full system profile and steps to reproduce.
If you are using a QCRenderer, the Patch Time is whatever you pass in
to renderAtTime:arguments: so any drift there would be a product of
the timers you are using.
Troy
On Dec 2, 2007, at 1:46 PM, Christopher Wright wrote:
Where is patch time derived from? It doesn't seem to be synced with
CFAbsoluteTimeGetCurrent().
To demonstrate this, create a system time patch(which uses
CFAbsoluteTimeGetCurrent()) and a patch time patch(which uses QC's
atTime: parameter I'm guessing), and plug them both into a math
patch that subtracts (giving the difference between system clock and
patch time). Then plug the math guy into an Image With String
patch, and finally to a billboard to see it go.
If patch time was synchronized with CFAbsoluteTimeGetCurrent(), the
delta would stay within a reasonable margin (depending on system
load and other external factors which I understand). However, the
actual results on my machine show that the delta decreases at a slow
rate (disregarding the ntpd time update things, as logged in
system.log). In other words, the two time sources are drifting.
The ntpd updates seem to take effect immediately, and cause a sharp
transition in the delta, so I'm guessing the ntpd delta isn't
smoothed out over time to cause this drift.
It's a really slow process, on the order of 0.001 seconds closer
every 10 seconds (0,001 seconds for the European readers :), so it
takes a bit of time to notice it.
So, to keep an external timer that doesn't drift relative to the
composition's clock, which time source should I use? (obviously not
CFAbsoluteTimeGetCurrent())
--
[ christopher wright ]
[EMAIL PROTECTED]
http://softpixel.com/~cwright/
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Quartzcomposer-dev mailing list ([email protected]
)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/quartzcomposer-dev/tkoelling%40apple.com
This email sent to [EMAIL PROTECTED]
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Quartzcomposer-dev mailing list ([email protected])
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/quartzcomposer-dev/archive%40mail-archive.com
This email sent to [EMAIL PROTECTED]
