[sf-lug] USB mic not working under 14.04

[Rick Moen]

Quoting Christian Einfeldt (einfeldt at gmail.com):

> I ran this command twice:
> 
> dmesg | tail -f
[...]


OK.
 
FYI, line-wrapping console output like that is bad, making it difficult
to visually parse, for no benefit.  Please avoid doing that, e.g., don't
use an ASCII editor that autowraps lines.  I've un-wrapped.

> me at mycomputer:~$ dmesg | tail -f
[...]
> [ 4751.061399] usb 1-1.4: new full-speed USB device number 3 using ehci-pci
> [ 4751.154774] usb 1-1.4: New USB device found, idVendor=0d8c, idProduct=000c
> [ 4751.154780] usb 1-1.4: New USB device strings: Mfr=0, Product=1, SerialNumber=0
> [ 4751.154783] usb 1-1.4: Product: C-Media USB Headphone Set
> [ 4751.156079] input: C-Media USB Headphone Set   as /devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.4/1-1.4:1.3/0003:0D8C:000C.0003/input/input13
> [ 4751.209702] hid-generic 0003:0D8C:000C.0003: input,hidraw2: USB HID v1.00 Device [C-Media USB Headphone Set  ] on usb-0000:00:1a.0-1.4/input3
> [ 4752.237430] usbcore: registered new interface driver snd-usb-audio
> me at mycomputer:~$

Yeah, there you go.  That's the thing, it appears?  Maybe?


> If I go to http://www.linux-usb.org/usb.ids and paste the suspected vendor
> ID into cntrl+F on that page, I get this info:
> 
> 0d8c C-Media Electronics, Inc.
> 
[...]
> 	000c  Audio Adapter
[...]


> Notice that the device shows up as an Audio Adapter, is that weird?

Does it look like the picture on this page?
http://karuppuswamy.com/wordpress/2010/10/04/how-to-get-usb-sound-adapter-0d8c000c-working-as-primary-sound-card-in-debian-linux/

The page concerns an outboard USB-connected rectangular sound gadget,
but the page says nothing about a microphone.

If the device you have does _not_ look like that, then maybe two
manufacturers are using the same VendorID:ProductID combo for two 
different USB devices.  That would be unfortunate.

Generically, there's a lot of USB-connectable devices that are not well
designed and made.  (No idea about your microphone specifically.)


> What might be the next step (if any) that I could take to getting this
> mic working?

Well, if it misregisters with the system USB controller chip as a
completely wrong device (if it looks nothing like the thing on that Web
page), then you have a seriously difficult problem.  

If on the other hand your device _does_ look like the picture on that
Web page, indicating that what you are calling a 'microphone' is
actually an external, USB-connectable full sound adapter with ability to 
drive headphones and microphones, then you need to set up PulseAudio or
whatever cruddy sound server *buntu is using these days.  This page
hints at that possibility:
https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/882734


> Rick had suggested just plugging the mic directly into the USB port, which
> I did for the second test above, and then I ran a third test with the mic
> plugged into the USB hub base.  Am I correct in saying that there appears
> to be no difference, in that the vendor and the device are still showing up
> the same?


If there were a difference, it would manifest as 'device doesn't register
at all when connected via USB hub', or 'doesn't do so reliably when
connected via USB hub', or 'misbehaves in operation in some way when
connected via USB hub', but these symptoms don't persist if _not_ using
the USB hub.  

This is why in _any_ USB debugging, pretty nearly the first suggestion
you will hear is 'Try again without the USB hub'.   I certainly would
not expect a USB hub to cause registration of a wrong VendorID:ProductID
combo, but, hey, bad things often happen with USB hubs generally, so
it's basic common sense to try without them (and to avoid them if
possible).