[Klug-general] Virtualbox woes

[Mike Evans]

Dan and I just had a convo on IRC but I thought I'd document the outcome 
for the benefit of everyone.  (Yes something that could go on the 
website, but not tonight, I'm tired.)

Basically if you have a usb sound device plugged in at boot the chances 
are the usb sound driver will get loaded before your regular sound card 
driver.  This has the effect of pushing your sound card driver from 
number '0' to number '1'.  Of course your alsa configuration has no way 
to know that's what happened and applies all the wrong settings to 
everything.

You can verify this by unplugging the USB device and rebooting and sound 
is probably restored as the sound card will be in the '0' position. 
Plug in the USB device after boot and it takes the number '1' slot and 
you're probably still good.  Reboot with it plugged in and they swap 
round again.  It would be possible to tweak your alsa configuration, but 
then it would be wrong if ever you booted without the usb device.

The answer for me was to dictate the order of the device numbers in the 
modprobe.conf file where I have the following lines:

alias snd-card-0 snd-ens1371
options snd-ens1371 index=0
options snd_usb_audio index=1

As a result of this my sound card with the ens1371 driver is 
consistently in position 0, and the webcam with its built in microphone 
is in position 1.

For some reason the speaker applet thingy on my gnome taskbar is still a 
little confused as it now always shows that the device is muted, but I 
get sound just fine.  I'll try to sus that out one day.

Incidentally there is a similar problem with the on-board modem driver 
module.  Even if you don't use it, if your distro ships with it it will 
probably load before the main sound card driver and then nothing works. 
  (You get some message about a semaphore not being ready in dmesg.) 
Ubuntu doesn't install the modem to sound card driver out of the box - 
but if you click on the 'install restricted drivers' bit for it then you 
will be in the same position as that's what happened to me on my laptop. 
  I believe there is a way to get them to load in the other order, but I 
found the web page once for it and can't track it down again.  The 
answer for me on this one has been to blacklist the modem bit as I don't 
need it right now.  The blacklisting is done using a similar mechanism 
in the modprobe file(s) and if anyone needs it I'll look it up on my laptop.

I had unpredictable sound card behaviour for ages before I discovered 
this stuff.  You can find it on various howtos and forums, but not all 
in one place.

The answer lies in doing an lsmod with the usb device plugged in at boot 
and one with it not there.  Compare the two and the additional modules 
are what's causing the problem.  You just have to figure out what to do 
about it.

MikeE


Dan Attwood wrote:
> after the discussion at the last meeting about virtualbox I decided to 
> give usb support another go.
> 
> I followed the various info on spodes site and on several other 
> resources and soon add usb support running and was was happily mixed 
> some banging tunes on with my usb mixer in propellerheads reason running 
> in seamless mode on windows xp.
> 
> and then I rebooted
> 
> oh dear
> 
> Now I get a message at boot time telling me that alsa failed to start. 
> Then when I get into gnome sound in totem doesn't work - the volume 
> slider is even greyed out. Sound in amarok is fine though. To add insult 
> to injury the usb support stopped work as well.
> 
> Anyone got any bright ideas?
> 
> 
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