For weeks I've been bedeviled by an audio bug on my MacBook Pro. The symptoms include poor audio quality by recipients of a Skype call using a USB microphone. While that may sound like an obscure bug, it affects one particular vertical market the hardest – podcasters.
Skype is the de facto standard software for podcasters who record their shows with guests in remote locations and the bug makes it virtually impossible to record a show. It usually rears its ugly head about three to five minutes into a Skype call. The people on the other end complain that you sound borg-like, echoey and full of static. Reboots and re-calls don't help.
It should be noted that I've spent weeks troubleshooting Skype, including, going all 802.11n, using a straight Ethernet connection out of my modem, removing everything else out of the mix (i.e. Vonage), switching Macs, even switching ISPs (from Verizon DSL to Comcast Cable) to no avail.
The good news is that I managed to isolate the problem last night while recording episode 75 of the PowerPage podcast. When I was originally complaining about the problem several fellow podcasters emailed me that there is a known issue with Core Audio in either 10.5.x or 10.5.2 (depending on who you ask) that affects Skype. But they mostly referenced it in the context of third-party audio equipment like USB and Firewire audio interfaces. M-Audio and Alesis devices seem to be especially effected.
After my MacBook Pro melted down on Monday I performed a "nuke and pave" (clean install) with the original installer DVD that came with the MBP - 10.4.9 (a.k.a. Tiger.) After installing the aging cat, I patched it up to 10.4.11 (but did not install the EFI firmware update) and lo and behold – it worked perfectly while recording my podcast over Skype last night.
With that I can confidently say that the Skype/Core Audio problem is definitely a Leopard bug. Chuck Freedman from my podcast was using 10.5.1 with a USB mic and insists that it's a bug specific to 10.5.2 (his audio was fine) so that's up for debate.
For the time being, this podcaster is sticking with Tiger.
Update: My microphone is a Blue Snowball (USB) which also appears to be part of the equation. I unplugged it and recorded episode 73 from the MBP's built-in mic using 10.5.2 and that worked. So, more accurately, the bug appears to be with 10.5.2 and a USB microphone.
Update 2: Adam Christianson from The MacCast sends this note from Alesis tech support:
"There have been reports like this from 10.4.10 to the present Mac OS as Apple made a critical change in its Core Audio drivers with the Leopard architecture. The way that we have found out to bypass this until Apple addresses this in a fix is to change the Audio Midi Setup menu options for input and output to 48k.
Have you been bitten by this bug?