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: Pete Gontier <email@hidden>
- Date: Tue, 09 Aug 2005 09:45:34 -0700
Title: Re: iTunes stuttering, and don't shoot me--it might involve Core Audio
When a CoreAudio client application offers control over audio buffering, the buffer in question resides within the application, not the system or the driver. (This can be confusing for Windows folk, because ASIO applications offer controls which do tweak the size of the driver buffer.) The problem could be the buffer iTunes allocates for use with CoreAudio, but, like you, I doubt it, and in any case iTunes would have to offer you control over this.
I too have had trouble with iTunes — in my case with a USB 1.1 disk. My library used to be encoded at 320 Kbps and stuttered occasionally even without writing activity (since the disk is entirely dedicated to my iTunes library). However, when I used iTunes to stream the same library on the same disk over the network, I got no such stuttering. This led me to believe the problem had something to do with iTunes file reading. I wrote an AppleScript to downgrade my library to 192 Kbps VBR, which seems to have worked around the stuttering problem at the expense of some audible-to-me encoding artifacts. I wish I had tried 224. Your mileage may vary.
— Pete Gontier <http://www.m-audio.com/>
From: Chris Luth <email@hidden>
Date: Tue, 9 Aug 2005 03:09:59 -0800
To: <email@hidden>
Subject: iTunes stuttering, and don't shoot me--it might involve Core Audio
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
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