Re: Interrupted audio
Re: Interrupted audio
- Subject: Re: Interrupted audio
- From: Jeremy Sagan <email@hidden>
- Date: Mon, 01 May 2006 20:28:48 -0400
Hello Jeff,
Please just answer this question. Is it possible to have a perfectly
well behaved and properly written program glitch simply because of
the Finder or some other application (or plug-in) accessing memory?
I quote you...
On Feb 15, 2005, at 2:36 PM, Jeff Moore wrote:
The VM Pager is one of the few threads that are actually higher
priority than a time constraint thread like what the HAL uses for
IO threads. So, if you have another thread that is page faulting,
it can and will interfere with the performance of the IO thread,
usually by pre-empting it or causing extra latency when scheduling
it.
When you say "if you have another thread" I think you mean "Another
system wide thread" since any thread can cause a page fault. Right?
Jeremy
On May 1, 2006, at 6:14 PM, Jeff Moore wrote:
One other thing, saying that OS 9 performed like you seem to think
it did, is also not quite right. OS 9 never ever performed in that
way. Glitching was just as likely there as it is on OS 9. In fact,
it was way worse judging from the bugs I had to fix there over the
years. I think you are looking at the past through some rose
colored shades =)
On May 1, 2006, at 3:07 PM, Jeff Moore wrote:
If you see a bug, you should file it so we can fix it. Otherwise,
my experience has been that nearly all overloads in applications
are caused by the actual app doing something stupid, like blocking
in the IO thread on that lock that they swear is never going to be
contended for or making an API call and not accounting for side
effects (like blocking).
I can't begin to count the number of developers who have said what
you are saying only to find that when they put a real magnifying
glass on their problem, it turns out to be completely their own
making. That's not to say that there aren't bugs in the OS. I'm
positive that there are, but saying things like this is not at all
helpful in tracking these bugs down be they in the OS or the
applications. Just wishing all the apps out there didn't have bugs
that cause glitching isn't any more helpful that wishing the OS
would wave it's magic wand and make all the problems go away.
So please, if you are seeing a problem and think it is in the OS,
document it, report it and we'll fix it. It's really that simple.
Given the state of the tools today, it's not even that hard to
document anymore. Between HALLab and Shark, folks should be able
to zero in on bugs like this pretty quickly.
On May 1, 2006, at 2:51 PM, Jeremy Sagan wrote:
I know I have written about this before and I love OS X in most
respects but it just seems like a step backwards from OS 9 with
the pervasive Core Audio overloads that could be caused by the
finder or any other process allocating memory. I am hoping and
wishing that Apple can address this system level issue in a
future OS update so we can go back to the days when we were
guaranteed that audio would play smoothly and without
interruption under normal operating conditions.
Jeremy
On May 1, 2006, at 5:07 PM, Kevin Avila wrote:
There is now a Technical Q&A online that explains overloads that
may be of help. http://developer.apple.com/qa/qa2006/qa1467.html
Kevin Avila
DTS Audio Engineer
World Wide Developer Relations
Apple Computer, Inc.
On May 1, 2006, at 2:02 PM, Jeff Moore wrote:
My guess would be that the app in question is experiencing
overloads. It would be easy enough to check using HALLab's
telemetry viewer.
On May 1, 2006, at 1:54 PM, david tay wrote:
I have an USB audio device that on occasion has 0s (zeros)
inserted into the output audio stream at higher sampling rates
(eg - 96khz), causing the audio to become interrupted.
What would be the likely causes?
--
Jeff Moore
Core Audio
Apple
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Jeff Moore
Core Audio
Apple
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