ISight microphone no longer available in Audio Preferences or iChat

Question

I have an iSight camera that was working with my Mac Mini when I first got the camera. But somewhere along the line the microphone vanished from the list of audio sources available in the Audio Preferences, or iChat, or anywhere else.
The camera works fine.
I just can't access the microphone.
The camera and microphone itself work fine when plugged into another computer. I even sent the iSight back to Apple, but the one I got back has the same problem, so it's something about my machine or the software environment.
I have been upgrading my software regularly, but I don't recall any correlation between an upgrade and the microphone stopping working. However, since I wasn't using the iSight regularly I could have missed this.
I see the Apple_iSight and AppleFWAudio kexts loaded:
neds_mini:~ ned$ kextstat | egrep -i 'Fire|FW|isight'
32 6 0x2dd06000 0x43000 0x42000 com.apple.iokit.IOFireWireFamily (2.0.9)
33 0 0x2dd6c000 0x1c000 0x1b000 com.apple.driver.AppleFWOHCI (2.5.2) <32 16 11>
67 2 0x329f4000 0x14000 0x13000 com.apple.iokit.IOFireWireAVC (1.8.1) <32 11>
69 1 0x32a37000 0x34000 0x33000 com.apple.driver.AppleFWAudio (1.1.3) <68 67 32 11>
80 0 0x3abb1000 0xa000 0x9000 com.apple.iokit.IOFireWireIP (1.3.4) <39 32 6 5 4 3 2>
101 0 0x3098a000 0x3000 0x2000 com.apple.driver.Apple_iSight (1.1.1) <32 16 11>
I have upgraded the firmware in the iSight. System Profiler reports:
iSight:
Manufacturer: Apple Computer, Inc.
Model: 0x8
GUID: 0xA270004000000
Maximum Speed: Up to 400 Mb/sec
Connection Speed: Up to 400 Mb/sec
Sub-units:
iSight Unit:
Unit Software Version: 0x102
Unit Spec ID: 0xA02D
iSight Unit:
Unit Software Version: 0x10
Unit Spec ID: 0xA27
iSight Unit:
Unit Software Version: 0x11
Unit Spec ID: 0xA27
iSight Unit:
Unit Software Version: 0x12
Unit Spec ID: 0xA27
Product Revision Level: 1.0.3
There are no interesting messages regarding the iSight in any of the log files under /var/log, AFAICT (from a grep, anyway).
Any suggestions?
Mac Mini   Mac OS X (10.4.5)  

Answer 1

... the microphone vanished from the
list of audio sources available in the Audio
Preferences, or iChat, or anywhere
else.Does that really mean that
when iSight is plugged in it is not an available
choice in the System Preferences... > Sound >
Input device list?
Yes, that's correct. The iSight is not visible in the System Preferences... > Sound > Input device list.
If so you may have a faulty Firewire cable.
I don't think so, because:
* This iSight works fine -- video and audio -- on another machine.
* The video and audio travels over the same data lines in the Firewire cable, and the video works fine. Cable problems would affect both audio and video.
Does "or iChat" mean, when iChat AV is the active app
and iSight is plugged in, that "iSight Built-in" is
not available in the iChat > Preferences... >
Video > Microphone: Choices Bar?
Yes, that's correct. The iSight doesn't appear in that list of choices.
When iSight is plugged in and iChat AV is the active
app, is there a tick (check) mark next to iChat >
Video > Microphone Enabled ?
Yes, but the menu choice is greyed out.
What other apps are "anywhere else": iMovie,
QuickTime Pro, what? Please list all apps you know
have the problem.
iMovie HD: can record from iSight, but there is no audio.
Garage Band: iSight is not available among the choices of audio inputs.
AU Lab (in Developer Tools): iSight is not available among the choices of audio inputs.
If you have added anything new to your Mac, consider
Possible hardware or software
conflicts.
Aren't there useful diagnostic logs somewhere? I'm used to copious debug output (from drivers, especially) when problems occur on my Linux systems. Is there somewhere to turn up the verbosity of the debug messages?
I sometimes get the feeling that the Mac is trying to hide important details about problems from me, and treating me like a baby. I mean, I have and know how to use a kernel debugger (though not yet on the Mac), oscilloscopes, and logic analyzers; I should be able to get the information I need to diagnose problems, rather than trying shotgun solutions.
If you haven't kept your Mac OS X maintenance up to
date, try that now.
I have repaired permissions; I will try a disk repair although I have no reason to believe that there are any file system problems (again, there are no debug messages in the logs that would indicate something like that).
Consider applying the 10.4.5 Combo Updater using the
method in How I Update My Mac OS X.
I'll try this too.
If you do not get help here or in Mac mini
Discussions, my only remaining suggestion is that you
take your Mac mini, iSight, and Firewire cable for a
professional check by your Apple Service Tech.
My nearest Apple Service Tech is over 50 miles away.
I'd prefer to find a fix here if I could.
Thanks for your help,
Ned