Re: unexpected webcam side effect

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On Saturday 07 July 2007 02:28, Tom Horsley wrote:
> On Fri, 6 Jul 2007 22:34:56 +0200
> Nigel Henry <cave.dnb@xxxxxxxxxx> wrote:
> > On Friday 06 July 2007 14:16, Tom Horsley wrote:
> > > Here's some behavior I've never seen before:
> > >
> > >
> >
> > I don't know about your problem specifically, but would you post the
> > output from.
> > cat /proc/asound/cards
> >
> > First do this booting up with the webcam unplugged, then shutdown, plugin
> > the webcam, reboot, and run cat /proc/asound/cards again.
> >
> > It will be interesting to see if, when the webcam is plugged in, it is
> > being detected as card0. ( that is, the usb mike part of it), and your
> > sound card is being set as card1.
> I added the above info to the bugzilla, but there is no card1, the nvidia
> sound just completely disappears.
> > Can you also post the output of /sbin/lsusb with the webcam plugged in,
> > and also the output from /sbin/lsmod.
> I think all the other info is already buried in some of the log files
> I added to the bugzilla.
> However, the most interesting fact so far is that if I rename the
> snd-usb-audio.ko kernel module so it can't be loaded, I can boot with
> the webcam plugged in, and everything (except, of course, the USB
> microphone) works fine.

>From what you say about renaming snd-usb-audio.ko, I think you may have run 
into an old problem, that used to be present on earlier versions of FC, but 
appeared to be fixed on FC4, 5, and 6. I've only just installed F7, but the 
problem has returned.

Basically the USB comes up early in the boot sequence, and anything that uses 
snd-usb-audio would be set as card0, and the sound card as card1. This was my 
experience with my usb midi keyboard. Alsa was trying to use it as a 

Looking now at how this problem has returned on F7. Cat /proc/asound/cards 
showed my usb midi keyboard as card0, and bt878 as card1, and my soundcard 
completely missing. bt878 is a module for the TV card, and is always 
problematic. Some distros create an index=2 for it, as it has a habit of 
grabbing card0. In my case it can't as the usb has already grabbed card0.

Ok. now for the fix, at least in my case. You need to add a couple of lines 
in /etc/modprobe.conf, as below.

alias snd-card-1 snd-usb-audio
options snd-usb-audio index=1

I also run as root. depmod -a after making changes to /etc/modprobe.conf.

That fixes the problem for me, and my modprobe.conf now looks like this, 
having added another options line for the annoying bt878.

alias eth0 8139too
alias scsi_hostadapter pata_via
alias snd-card-0 snd-emu10k1
options snd-card-0 index=0
options snd-emu10k1 index=0

alias snd-card-1 snd-usb-audio
options snd-usb-audio index=1

options snd-bt87x index=2

It's worth a try Tom. Just rename snd-usb-audio.ko back to it's original name, 
add the 2 lines to /etc/modprobe.conf, plug in the webcam, and reboot.

All the best.


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