Re: iTunes stuttering, and don't shoot me--it might involve Core Audio
Re: iTunes stuttering, and don't shoot me--it might involve Core Audio
- Subject: Re: iTunes stuttering, and don't shoot me--it might involve Core Audio
- From: Jeff Moore <email@hidden>
- Date: Tue, 9 Aug 2005 15:12:59 -0700
Without going into the possible reasons for them (there are a myriad
of possibilities), glitches usually manifest themselves as an
overload or other anomaly in the HAL. The best tool to use to observe
the HAL is HALLab's IO cycle telemetry. The telemetry lets you hook
into a target app and snoop on what the HAL is up to. It also lets
you take latency traces based on telemetry events. Between the two
kinds of data you should be able to get a pretty darn good idea about
why something is glitching.
Plus, you end up with some solid data on which to base a bug report
when you file a bug about the problem.
On Aug 9, 2005, at 4:09 AM, Chris Luth wrote:
An old customer service adage says that for every one person who
complains, there are 99 others who feel the same way but keep
quiet. I think this is magnified by 100 for computer-related issues.
Well, several of us over on the Apple Discussion board have
encountered a problem where iTunes "stutters"--that is, playback
pauses for an annoying brief fraction of a second. I and a few
others have found that it happens any time there is a spike in disk-
writing activity. (It doesn't have anything to do with CPU usage,
as far as we can tell.) I'm thinking that iTunes doesn't maintain a
very large buffer for data read off of disks.
So why am I submitting this to the Core Audio API list?
Because I've found you guys helpful in the past (I used to lurk a
bit and then unsubscribed when life got hectic).
But more than that, I still harbor some suspicions that it *might*
have something to do with a too-small Core Audio buffer, but I
can't find a way to tweak the overall system audio buffer. (I know
you can tweak the recording buffer in individual apps like Logic
Pro and Soundtrack Pro. I have both--I'm a broadcast journalism
major.) Here's the interesting thing, though: iTunes, as well as
QuickTime Player, DVD Player, RealOne and Windows Media Player all
stutter on--guess what--Internet-streamed media. Surely disk
writing wouldn't affect that...
On my machine, it stutters using the built-in speakers, the line-
out, and on my Mackie Onyx 1220 that I have hooked up via FireWire.
(A huge thank you, Core Audio folks, for creating this wonderful
system that allows me to easily do multichannel I/O!!!)
Check out the thread at the Apple Discussion Boards: http://
discussions.info.apple.com/webx?email@hiddenFmb3mj.8@.68aca9a0
They're also complaining about it over at Mac OS X Hints: http://
www.macosxhints.com/article.php?story=20050623234932431&query=itunes
+skip
Any insights you might have would be helpful.
Thanks,
Chris
--
Jeff Moore
Core Audio
Apple
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