In several previous posts I gave detailed instructions on how to use Soundflower with ustream.tv and other arcane audio mixing topics under MacOS X.
While these tricks sort of worked, I always had problems with audio after a while. I thought I'd be able to fix it with a change in buffer size or something similar, but I can't, and now I know why -- the problem seems to be isolated to Soundflower. Upgrading to the latest version, 1.4.3, doesn't fix the problems.
It seems that even running Soundflower on my wife's MacBook with no special hardware or audio applications -- just iTunes -- it is pretty easy to get Soundflower to go crazy. Set up the default audio output to be the two-channel Soundflower bus. Run Soundflowerbed and tell it to send the two-channel output to the built-in output. Now play some music. You'll probably have to play with some volumes using Audio MIDI Setup and iTunes.
On my wife's MacBook, plugging in a pair of headphones, which should just result in diverting the audio going through the speakers to the headphones, sends Soundflower into a tizzy -- I start hearing garbage through the headphones, the telltale "buzz" or stutter that tells me that it is playing one buffer of audio in a tight loop, and not getting any fresh audio streaming in. Setting the output to "None" and back to "Built-in Output" fixes the problem reliably.
On my Mac Pro, the problem is even worse -- I don't have to touch anything for the audio to become trash. Just letting iTunes run through my Apogee Ensemble via Soundflower results in the audio failing after a minute or two. Turning the Soundflower output off and back on seems to reliably fix the problem, but it's unusable when I have to fix it every couple of minutes; I can't do a live performance that way.
Interestingly enough, it seems to be just the monitoring of the Soundflower bus via Soundflowerbed that fails; ustream's meter shows the audio still going out.
There are some other issues but this one is a show-stopper. So unfortunately I can't recommend Soundflower for the time being, and I don't really have a workaround. If anyone knows of a similar tool that will give me an extra virtual audio bus that I can use to record or stream, I'd love to hear about it.
I've reported this issue to the developers, and I note that another user is also reporting trouble with the Ensemble. I don't think it is the Ensemble's fault, though, given the way the failure occurs on a stock MacBook. The developers do not seem to be responding to recent bug reports at present.
I'm about to install the 10.5.7 system update; we'll see if that improves the situation.
Soundflower is open source. About 8 years ago I worked on CoreAudio drivers for a commercial PCI-based audio interface, so in theory I should be able to dig into the Soundflower code base and, with luck, figure out what is happening and help fix it. In practice debugging this sort of thing could be a major time sink, and given that I'm already working more than full time and a parent, it seems unlikely that I can make any headway in that direction, but if I get some down time I'll see what I can do.