FIXED: Boot Camp Audio Pops and Crackles with Windows 7 x64

Speaker_IconI have passed the 96 hour mark with a working fix for my audio problems with Boot Camp 3.1 running Windows 7 x64. To recap, I recently did a fresh installation of Windows 7 on my Mac Book Pro unibody (late 2009). Afterward, I started getting audio anomalies in the form of loud pops and permanent crackle distortions. These went away if I restarted audiosrv or reset the drivers in any way. For example, unplugging and plugging the speakers back into the minijack would fix it for a while as would turning audio enhancements on and off in the control panel for one of the devices.

I tried getting the latest Crystal Audio driver from Apple and  a solution from the interwebs that suggested disabling 802.11a. I also dug up a much newer version of the Broadcom wireless network card driver than Apple is distributing. I tried fiddling with Skype, which seemed to be part of the problem. I also disabled the USB audio device in my Apple Cinematic Display. None of these interventions totally solved the problem.

Then I came across a KB article that describes a similar but different issue with USB audio:

  • You attach a USB audio device to a computer that is running Windows 7 or Windows Server 2008 R2.
  • You configure this device as the default audio device.
  • You put the computer into the S3 sleep mode while an application plays audio.
  • You disconnect the USB audio device while the computer is in the S3 sleep mode.
  • You resume the computer from the S3 sleep mode.

In this scenario, the application that was playing audio stops responding. Additionally, all the other audio-related applications stop responding. For example, Volume Mixer also stops responding.

This is similar. My problems with mangled audio seemed to be related to power management, sleep yes but also not exclusively. My symptoms were much less extreme than the ones described: corruption instead of outright failure. The hotfix replaces the usbaudio.sys driver that shipped with Windows 7/2008R2 gold with a new version from July 14, 2010. What the heck, usbaudio.sys, is being used by one of the audio devices so I decided to give it a try.

Viola. It fixed my issue. I have had no audio squirreliness in 4 days where I previously could not have gone 4 hours.

What has me really scratching my head is how did I not have this problem before? I was running Windows 7 for a year on this computer and I didn’t really notice much of an audio problem until two weeks ago. Maybe it is the sort of thing that you don’t notice until you do and then you really notice.

Microsoft KB article 2122063: “The audio applications stop responding in Windows 7 or in Windows Server 2008 R2 after you resume the computer from the S3 sleep mode”

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Why is Skype Using the Wrong Audio Device?

I’ve been trying to figure out what is causing my audio to whack out and go crackly intermittently. Now I’m hyper-sensitized to anything making pops and crackles on my late 2009 MacBook Pro 15” running Windows 7 x64 with Boot Camp 3.1.

One thing I noticed is that the pops seem to always start with the incoming IM noise emitted by Skype. Another thing I noticed was that the pop seemed to be first coming from my 24” Cinematic Display. To simplify the number of things going on, I disabled the Cinematic Display (aka "Apple USB audio device”) and “Digital Audio (S/PDIF)” playback audio devices in mmsys.cpl because I’m not using them. (I’ve gone many hours without any pops and crackles after disabling these two devices but I’m not ready to say the problem is solved.)

What I just noticed is that the incoming IM ping sound was coming very much from my right speaker and it was really loud. Then I realized it wasn’t coming from the right desktop speaker at all. It was coming from my laptop. All of my other sound is coming out of my Klipsch speakers via the “headphones” minijack. Nothing should be coming out of the laptop speakers which aren’t the current default playback device. It shouldn’t be doing that.

The Volume Mixer shows that Skype is the only thing using the built-in speakers. These screenshots were taken nearly simultaneously without making any system changes. I just changed the selected device in the Volume Mixer.

skype-using-interanleverything-else-using-default

All of the Skype incidental notifications are coming out of my laptop but voice calls are playing out of the configured default playback device, which is my desktop speakers. Very weird. This reminds me that when we first got the MacBooks it was just as Snow Leopard was released and we had the drivers in Boot Camp 3.0. Skype could not hear anything with the built-in microphone even though the built-in microphone was working as demonstrated by Sound Recorder.

I have a suspicion that Skype is doing something low-level and inadvisable with the audio devices.

For the record, according to Skype’s own settings dialogs, it should not be using the laptop built-in speakers.

skype-audio-config

Mystery Solved!

The notifications show up on whatever speaker is defined in Options | Audio Settings | Ringing. By default that is set to “Ring on all devices”. Changing it to Use selected speaker removes the weirdness of ringing coming out of the laptop speakers while using headphones.

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