Re: Another audio latency question: 43 frame offset?
Re: Another audio latency question: 43 frame offset?
- Subject: Re: Another audio latency question: 43 frame offset?
- From: Bill Stewart <email@hidden>
- Date: Tue, 27 Nov 2001 16:36:05 -0800
Yes, we've seen this as well and are actively investigating it to
see what the problem is. We'll keep you posted - we saw the same
numbers as you have as well.
Thanks for your information...
Bill
On Monday, November 26, 2001, at 06:05 AM, Kurt Revis wrote:
So I'm playing around with some code to test the latency and
timestamping of the audio system and hardware. I'm running a cable
directly from my computer's output back into its input. Then I
play a tick on the output, and listen for the tick in the input.
This seems simple enough.
The weird thing is that the timestamps of these two events are
always 43 frames apart! From what I understand about CoreAudio's
timestamping system, I would expect the times to be the same. My
understanding is that the timestamps indicate exactly when my
audio will be played, and when it was received (right?).
(I might expect the timestamps to be off by a frame or two, to
account for random analog hardware slop. But 43 frames seems like
a long time to me--almost a millisecond.)
Can anybody explain to me where this 43 frame offset is coming
from? Is this just a property of the way the audio hardware works,
or am I misunderstanding things?
Details: I get the same results on both a G4/450 tower and a Pismo
PowerBook, both using the built-in audio hardware. Daisy shows the
"input latency" and "output latency" to be 0, and the safety
offset to be 16 frames.
My app's buffer size doesn't have any effect on the 43 frame offset.
Thanks to anyone who can provide illumination! (Yes, I'm full of
questions today...)
--
Kurt Revis
email@hidden
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