NOTE: Seems as if Apple really got the problem fixed with the Mac OS X 10.4.5 update. Hooray.

I have been suffering from a bug that affects my brand new 15″ PowerBook machine and it seems to affect this machine only as I haven’t experienced that bug on any of my other Macs and I know quite a few people with the same model that recently ran into exactly the same problem. Here is a short sample of the bug that I accidently recorded in my Chaosradio Express 003 podcast episode (german only and a really weird one a it was all about testing things ;). Here is another example I found in an ongoing discussion in Apple’s forums.

Recently, the same bug occured to Adam Curry in episode #309 of his Daily Source Code podcast. I wrote an e-mail to Adam and he talked about it in episode #311 two days later. Another podcaster provided an audio comment on the same issue as well.

Update: I have filed a bug with Apple (Problem ID: 4402288). If you have an ADC account (which is free) you might want to refer to that bug.

Update 2: The update to Mac OS X 10.4.4 and QuickTime 7.0.4 did NOT solve the problem. Damn.

Update 3: Apple has posted a tech support Article #302978: „PowerBook G4 (Double-Layer SD) audio stutters or skips“. For my part I can say that the problem occurs even when I am only running Ableton Live with no other applications running at the same time whatsoever. At least Apple has confirmed there is a problem and it actually seems to be tied to the 15″ PowerBook G4 only as expected. The document closes with „This document will be updated as more information becomes available“. Well, Apple, we keep an eye on that.

Update 4: So far I thought the problem is related to sound being sent to the built-in audio port only. But I recently encountered the audio loop problem in a setup where Ableton Live sent audio to QuickTime Broadcaster via the Soundflower virtual audio port. This seems to indicate the problem is related to software instead of hardware as the built-in audio port was not used in this setup. However, it might still be related to some kind of internal timing-related hardware.

Update 5: There is a new activist site dedicated to the problem at http://powerbookdefect.info/ (or http://maclantic.com/powerbookdefect/The%20Defect.html if you don’t like frames). If you have the same problem, you can add yourself to the list. The story has been dugg. Digg it!.

Update 6: HardMac.com is taking up on the story. Please let all other news sites know about this as well. The list of affected users on powerbookdefect.info has grown to more than 800 now.

Update 7: ZDNet.com is summarizing the disaster so far adding well-known display and DVD problems to the list. I haven’t had any of the display and DVD problems but I haven’t done so much DVD stuff recently as well so it might well be that more problems are ahead.

Update 8: According to a posting at Macintouch, an Apple employee at an Apple Store promised a solution to the problem „within a week“. We’ll see. Obviously the problem has received at least some attention at Apple.

Others have been reporting about the bug as well:

• PowerBook G4: Audio Problems (was: Macintouch: PowerBook G4 (Part 37): Audio Problems)
• I’m Having the „Audio Echo“ Problem with My New PowerBook
• A Possible Fix for the 15-inch PowerBook „Audio Echo“ Problem (the fix didn’t work for me)

I know the Ableton tech support guy is suffering from the same problem.

So what is it all about?

This is what happens: Out of the blue, the Mac suddenly starts looping all the audio that goes out to an audio device. This usually last for around five seconds, effectively adding all audio being sent to that device playing everything over and over again at the same time increasing overall volume and creating a crazy and confusing mix that disappears after five seconds.

The bug seems to be related to CoreAudio as this is the subsystem managing audio devices. It does not seem to be tied to a certain application as I noticed the bug using iTunes, Ableton Live, QuickTime Player and other programs. There is no obvious event that triggers the bug, it just happens. Sometimes the event repeats within minutes two or three times and then again the bug is not coming at all for days. It is so annoying.

My configuration is the following:

• Most recent Macintosh 15-inch PowerBook G4 (1440×960 display, optical audio)
• Mac OS X 10.4.3
• 2 GB RAM (I doubt the bug is related to RAM as the recent WLAN stability bug was)

Apple does not really promote a distinct name for the PowerBook generation introduced in October 2005 but I refer to it as the PowerBook with „Optical Digital Audio“ as it is the first Apple laptop to feature optical audio input and outputs. Read about it on Apple’s developer site. The most visible difference is of course the bigger screen size.

Main problem here is reproducing the problem. I haven’t found a way to do that so far and I am open for any suggestions. I think is related only to audio output as I haven’t experienced the bug when recording audio so the bug seems to not be affected to audio input. I only have been able to record the bug while producing audio feedback during the above session because I had loudspeakers running during the recording (as I did not have extra headphones for my guest).

So what can be done? I’d be happy if you would share your experiences with me here in this blog. I am going to reintegrate all feedback in this post to make the description as complete as possible.

If you find your podcast being listed on Creative’s new Zencast site, I would consider writing them an angry e-mail now as they are basically hijacking your feed: people who subscribe through the Zencast site get a subscription URL of zencast.com instead of your original feed. This means that they can track your stats, filter or modify your content and that your subscriber’s not only depend on the stability of your server but on the zencast site as well.

Really bad self-introduction to the podcasting scene, Creative. Better quit now before it’s too late. Nobody is buying your ugly players anyway.

Update: It seems as if they have given in and changed the behaviour. Zencast now hands out the original feed as it has to be. Good boy.

Adding to my other plea regarding integrating BitTorrent in iTunes, I’d like to add that I think that BT might make downloads much more robust over unreliable and slow Internet links. I am currently behind a really flaky Internet connection and there is just no way downloading larger files at all. Half way thorugh, downloads get terminated and iTunes tries to start all over again. Continuing http downloads from where they left off might be a way to do it, but this is not very reliable in case the target file changes on the server (I agree this does not happen often but I just did that myself a few times for various reasons and it must be taken into account).

Best thing about BT is that it splits up the file in smaller chunks that are each secured by a checksum. So downloads can be done incrementally and (more or less) securely.

The December 28th edition (MP3, 7,2 MB) of 2600’s Off The Hook radio series was done live from the 22nd Chaos Communication Congress using our DECT phone system and the Internet-based dial-out feature. It’s a one hour show. The first part focuses on the event itself, the rest is about other topics.