System: NEC Versa M540 laptop
Dist: Debian Sarge/Etch
Kernel: 2.6.18
Alsa: using drivers in kernel, although no difference when compiled from
alsa-source package.
Card in question: C-Media USB sound card (more info below)
I recently purchased a C-Media USB sound card, and eventually figured
out that it only works with a fragment size of 2048 or less. I can use
alsaplayer with the '-f' option to hear sound through them, but I want
to tell ALSA in general that it can only handle this range for the
fragment size (and only for this card). Hopefully then I'll be able to
hear all my other applications.
I'm not even sure where to start -- udev, ALSA configuration, module
configuration...
I've read every resource on ALSA configuration files that I can find,
and tried a whole lot of plugin definitions and parameters with no luck
whatsoever. I also tried forcing the index of the card by adding the
following to /etc/modprobe.d/alsa-base, but even this only works half of
the time:
--
# Prevent abnormal drivers from grabbing index 0
options snd-bt87x index=-2
options snd-cx88_alsa index=-2
options snd-atiixp-modem index=-2
# options snd-intel8x0m index=-2
options snd-via82xx-modem index=-2
options snd-intel8x0 index=0
options snd-intel8x0m index=1
options snd-usb-audio index=2 vid=0d8c pid=000c
options snd-usb-audio index=3
--
The contents of '/proc/asound/cards' are:
--
0 [I82801DBICH4 ]: ICH4 - Intel 82801DB-ICH4
Intel 82801DB-ICH4 with ALC655 at 0xf0000400, irq
5
1 [Modem ]: ICH-MODEM - Intel 82801DB-ICH4 Modem
Intel 82801DB-ICH4 Modem at 0xe200, irq 5
2 [default ]: USB-Audio - C-Media USB Headphone Set
C-Media USB Headphone Set at usb-0000:00:1d.1-1,
full speed
--
...although sometimes the ICH-MODEM is missing and the C-Media card is
at #1.
Card information from 'lsusb':
Bus 002 Device 003: ID 0d8c:000c C-Media Electronics, Inc. Audio Adapter
Usually I boot with the card plugged in, but if I plug it in after
booting, the new modules loaded are: snd_hwdep, snd_rawmidi,
snd_usb_audio and snd_usb_lib.
By the way, nowhere could I find in the documentation what the various
synonyms were for 'fragment size' -- what else is this parameter called?
What is the equivalent in ALSA configuration files? I figured it was
'packet_bytes', but I wasn't sure.
Anyway, I would appreciate any advice on this.
Thanks,
Jason
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