Bad Recordings Under Windows (High Geek Content)

Chris Clementson · **Voice Seeker** Joined: 14 Jan 2008 Posts: 216

I have come across some interesting information regarding audio playback and Windows. If it applies to audio playback, it follows that real-time audio recording would be affected as well.

Mark Russinovich of Microsoft says that media playback can be affected by network activity. When a network packet arrives, it triggers a CPU interrupt and triggers an Interrupt Service Routine which blocks other device interrupts, including sound cards and audio interfaces. Servicing network packets can, at times, take precedence over all other thread execution, thereby impeding media playback (and, one assumes, recording as well). Russinovich says that copying a file from one machine to another (over a network) can consume 41% of the available CPU cycles.

A couple of weeks ago I was testing a mic and I couldn't get through 15 seconds of copy without getting all kinds of pops and clicks in the audio. A few days earlier, Windows Update had installed an updated wireless networking driver on my machine, and in the process did me the unrequested favor of re-enabling wireless networking (I previously had it disabled). I checked the wireless network settings and re-disabled it. Voila! No more pops and clicks in the audio. Coincidence?

The simple workaround is, if you're getting pops and clicks in your audio recordings, try disabling both wired and wireless networking and see if it helps. 41% of your CPU is an awful lot to lose. Supposedly Linux handles network traffic much more gracefully.

Read more about it here:

http://blog.rlove.org/2007/08/those-dang-dpcs-clogging-mmcss.html

Lee Kanne · Posted: Tue Jan 29, 2008, 23:52 (GMT) Post subject:

There's a lot of info on the web about how to optimize Windows XP and your PC for running audio...here's one of them:

http://www.audioforums.com/resources/windows-xp-optimization.html

disabling the network card is one of the tweaks mentioned..

Chris Clementson · **Voice Seeker** Joined: 14 Jan 2008 Posts: 216

I'm surprised to see they recommend disabling the swap file. I disabled mine and my computer hasn't blown up yet -- but then I've got it maxed out at 2 GB.

I'm not sure when they introduced it, but Audacity now enables caching of audio data to RAM. This is a wonderful thing as there is less overhead involved in writing to RAM than to hard disk.

Lee Kanne · Posted: Fri Feb 01, 2008, 04:09 (GMT) Post subject:

as a rule of thumb, disabling virtual memory is not recommended unless you have at least 1GB RAM loaded..

Chris Clementson · **Voice Seeker** Joined: 14 Jan 2008 Posts: 216

Lee Kanne · Posted: Sat Feb 02, 2008, 06:03 (GMT) Post subject:

Ah, the beauty of a Mac

Chris Clementson · **Voice Seeker** Joined: 14 Jan 2008 Posts: 216

The last time I recorded audio with Audacity on OS X I got a nice, unexpected click, so Macs are not immune from dropouts, either.

Lee Kanne · Posted: Sat Feb 02, 2008, 17:30 (GMT) Post subject:

as you well know, pops and clicks and come up for a variety of reasons....some not having anything to do with the OS

I've found macs to be pretty much plug and play when it comes to audio....

Chris Clementson · **Voice Seeker** Joined: 14 Jan 2008 Posts: 216

I'm glad you've had good experiences with Macs, but to suggest they are a panacea would not be accurate in my experience. Audio dropouts generally occur because the CPU isn't available when the audio stream needs it.

In the paper I linked to it states that Linux, which now has a real-time kernel, puts far less of a drain on the CPU when performing networking tasks. Whether this will result in click-free recordings every time remains to be seen. I don't know about the kernel used in the OS X version of Unix. I can't figure why anyone would need to be on a network when recording audio in the first place, but I can see where people might listen to audio while surfing the web, etc.

Lee Kanne · Posted: Sat Feb 02, 2008, 23:13 (GMT) Post subject:

yes, I have had mac issues in the past, no question...most of my issues however, have had to do with trying to fit a square peg in a round hole, like trying to run Tiger on an old G3 with limited RAM, or something to that effect..

I will say though, that I have never had to disable my Airport card while running sessions..

I don't want to get into the dreaded Mac vs PC discussion here, because there really is no clear winner...Macs aren't as suseptible to viruses, so you don't have all that annoying anti virus software to worry about, they don't take anywhere near the configuring that PC's do to get you up and running and recording audio, but Macs are expensive, are a closed system, and have fewer software choices..plus, you are a slave to whatever hardware externals are compatible with your new Mac, (like not being able to use your old PCI audio card or your SCSI drives)..