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MultipleCards

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Naming multiple audio devices has always been a hot issue, until recently. This article tries to clarify the recommended ways to use and name multiple devices.

If you have multiple sound cards, or audio on the motherboard and an external sound card, ALSA may not use the devices you prefer.

Contents

See what's going on

See Troubleshooting to play a file and see which card ALSA uses.

At a low-level, the files cards, modules, and devices in the directory /proc/asound show how ALSA has configured itself.

Strategy

You can either modify a user's .asoundrc file to tell ALSA that user's preferences for cards, or alter how ALSA loads modules and drivers.

Understanding /etc/modprobe.d/alsa.conf

/etc/modprobe.d/alsa.conf (or /etc/modprobe.d/alsa-base.conf or similar) is the main ALSA configuration file in most linux systems. Its syntax and all the options and parameters are explained in /usr/src/linux/Documentation/sound/alsa/ALSA-Configuration.txt. If you don't have the kernel sources, you will find this file with the documentation of the alsa-driver package.

You will need root permissions to modify this file; one way is to prefix each command here with sudo. After modifying the configuration file, you need to reboot your computer to see the effect; you may be able to preview the effect by restarting ALSA with a command like (as root)

/etc/init.d/alsasound restart

or possibly

/sbin/alsa force-reload

alsa.conf structure

The content of alsa.conf can be separated into a few sections.

# ALSA portion
alias char-major-116 snd
alias snd-card-0 snd-ice1724

This will load the core ALSA module as well as the module for an Audiophile 192. When more than one card, add a line for each card. (Even a webcam with a mic is a sound card for ALSA.)

# module options should go here
# actual card's number [default=1]
options snd cards_limit=1
# card(s) specific options
options snd-ice1724 index=0 model=ap192

This will load the wanted options for the different modules. Multiples options for different cards with the same modules can be defined as follow:

options snd-usb-audio index=1,2 vid=0x0ccd,0x0d8c pid=0x0028,0x000c

This will define 2 usb sound cards, the first one at index=1, vid=0x0ccd and pid=0x0028; the second one at index=2, vid=0x0d8c and pid=0x000c.

# OSS/Free portion
alias char-major-14 soundcore
alias sound-slot-0 snd-card-0

This will load the main aliases and modules for OSS-emulation. Add one sound-slot-n line for each subsequent card.

# OSS/Free portion - card #1
alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-oss
alias sound-service-0-12 snd-pcm-oss

This will load the aliases for the first sound card.

Each subsequent card must have something like the following:

# OSS/Free portion - card #2
alias sound-service-1-0 snd-mixer-oss
alias sound-service-1-3 snd-pcm-oss
alias sound-service-1-12 snd-pcm-oss

Problems with alsa.conf and udev

On modern GNU/Linux systems, udev takes care of discovering hardware and loading/unloading Alsa. There is one drawback to udev. Udev will load Alsa modules in an undefined order. After each reboot or plugging/unplugging a device, there is no guarantee that a device is renamed using the same hw:x,y numbers. For example, if you have two USB devices on your systems, for example an Audeon USB and an Edirol UA-25, after each reboot, a card can be "hw:0,0" and the other "hw:1,0", each time randomly.

/etc/init.d/alsasound is an udev wrapper that will take care of loading the ALSA modules during booting. But even with it, a few problems may still occurs.

Reordering the driver for a particular card

You can tell /etc/modprobe.d/alsa.conf (or alsa-base.conf, or similar) to keep a driver in out of the default slot. For example, if you have a a Creative Labs soundcard driven by the "emu10k1" driver and you don't want it to be your default card 0, append

options snd slots=,snd-emu10k1

Note the comma in this line that moves the driver to the second slot.

Module ordering problems

It may be that the sound card order is wrong after booting, but running (as root)

/etc/init.d/alsasound restart

or

/sbin/alsa force-reload

gives the wanted card order.

This can happen because udev is loading some sound driver before alsasound, and alsasound gets confused. A restart will first unload all the sound modules and when restarting, alsasound will work as expected.

The solution is to blacklist the module(s) that udev is loading before alsasound (Typically, the one you get as sound card 0 after booting). You must do this into

/etc/modprobe.d/blacklist.conf

You must also report it as a bug to your distribution.

Understanding Alsa naming

Single device

Originally, Alsa was only able to name an audio device using the hw:x,y syntax, where x and y are numbers.

For example, if there is only one device installed, in most cases, the device should be named hw:0,0. When there is only one device, the device should always have the same name and numbers.

Multiple devices

Running aplay -l dislays a list of PLAYBACK Hardware Devices. For example, on my system:

$aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: UA25 [EDIROL UA-25], device 0: USB Audio [USB Audio]
 Subdevices: 1/1
 Subdevice #0: subdevice #0
card 1: Audio [USB Audio], device 0: USB Audio [USB Audio]
 Subdevices: 1/1
 Subdevice #0: subdevice #0

In this example the audio devices are named "UA25" and "Audio".

Example commands and options for selecting sound cards:

Note options: -d device | device_alias -- Please see man aplay and man alsaplayer for an explanation of the options.

alsaplayer -o alsa -d UA25  some_k00!.ogg
alsaplayer -o alsa -d hw:0,0  some_k00!.ogg

How to choose a particular order for multiple installed cards

Which card is card number 0, 1 and so is by default determined by module load order. This is particularly useful to choose which card becomes the default one.

In theory therefore it is possible to choose which of several installed cards becomes card 0, the default one, by ensuring its driver module is loaded first. (Note: this assumes that each sound card requires a different driver. If you have two soundcards of the same type, please skip to the next section.)

There are two ways to achieve this, the "old" index= option of the card driver module, and the alternative (and new) slots= option of the snd module.

The older "index=" method

An example configuration for two sound cards is like below:

# ALSA portion
options snd cards_limit=2
alias snd-card-0 snd-interwave
alias snd-card-1 snd-ens1371
options snd-interwave index=0
options snd-ens1371 index=1
# OSS/Free portion
alias sound-slot-0 snd-interwave
alias sound-slot-1 snd-ens1371

The newer "slots=" method

Alternatively, you can use the slot option instead of the index options:

options snd slots=snd-interwave,snd-ens1371

Then, the first slot (#0) is reserved for snd-interwave driver, and the second (#1) for snd-ens1371. You can omit index option in each driver if slots option is used (although you can still have them at the same time as long as they don't conflict).

According to ALSA-Configuration.txt, The slots option is especially useful for avoiding the possible hot-plugging and the resultant slot conflict. For example, in the case above again, the first two slots are already reserved. If any other driver (e.g. snd-usb-audio) is loaded before snd-interwave or snd-ens1371, it will be assigned to the third or later slot.

\

Ordering multiple cards of the same type

If you have more that one sound cards which use the same modules, you may want to define the card order. This can be done by specifying index and ID options to the module being loaded. For example,

options snd-usb-audio index=1,2 vid=0x0ccd,0x0d8c pid=0x0028,0x000c

This will define 2 usb sound cards, the first one at index=1, vid=0x0ccd and pid=0x0028; the second one at index=2, vid=0x0d8c and pid=0x000c. The vid and pid here were discovered using lsusb.

The documentation may not be entirely up to date and comprehensive. The command

modinfo -p ${modulename}

shows a current list of all parameters of a loadable module.

Example:

# modinfo -p snd-usb-audio
ignore_ctl_error:Ignore errors from USB controller for mixer interfaces.
device_setup:Specific device setup (if needed).
async_unlink:Use async unlink mode.
nrpacks:Max. number of packets per URB.
pid:Product ID for the USB audio device.
vid:Vendor ID for the USB audio device.
enable:Enable USB audio adapter.
id:ID string for the USB audio adapter.
index:Index value for the USB audio adapter.

In this case, the pid and vid options from lsusb can be used. See MultipleUSBAudioDevices

But, consider this PCI device,

# modinfo -p snd-ice1724
model:Use the given board model.
enable:Enable ICE1724 soundcard.
id:ID string for ICE1724 soundcard.
index:Index value for ICE1724 soundcard.

In this case, there is no option that can be used to define the sound cards order for multiple ICE1724 sound card. I see no other way than with a specific udev rule. See Udev.

\

Why doesn't this code work when using newer ALSA versions?

The syntax for the module options has changed. Now you have to write all options without the leading snd_. Example: only index=0 instead of snd_index=0.

Stephan Wurm

Some examples configurations

Loading the kernel modules for multiple cards

Frank Barknecht offered this dual card configuration example to the alsa-devel mailing-list.

See TwoCardsAsOne for an idea for setting up an .asoundrc to use two cards together. Read chapter below (a code fix).

# START
alias char-major-116 snd
alias char-major-14 soundcore
options snd snd_major=116 snd_cards_limit=3 snd_device_mode=0660 snd_device_gid=29 snd_device_uid=0

# Midiman
alias sound-slot-0 snd-card-0
alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-oss
alias sound-service-0-12 snd-pcm-osshree 

# SBLive
alias sound-slot-1 snd-card-1
alias sound-service-1-0 snd-mixer-oss
#alias sound-service-1-1 snd-seq-oss
alias sound-service-1-3 snd-pcm-oss
#alias sound-service-1-8 snd-seq-oss
alias sound-service-1-12 snd-pcm-oss

# VirMIDI
alias sound-slot-2 snd-card-2
#alias sound-service-2-1 snd-seq-oss
#alias sound-service-2-8 snd-seq-oss

#alias snd-card-0 snd-card-ice1712
alias snd-card-0 snd-ice1712
options snd-card-ice1712 snd_index=0 snd_enable

#alias snd-card-1 snd-card-emu10k1
alias snd-card-1 snd-emu10k1
options snd-card-emu10k1 snd_enable

#alias snd-card-2 snd-card-virmidi
alias snd-card-2 snd-virmidi

post-install snd-synth-emu10k1 /usr/bin/sfxload /dos/audio/sblive/SFBank/8mbgmsfx.sf2
# END

Multiple Sound Cards -- Example on Debian GNU/Linux

RE: How do I use this?

Lines such as found in the multiple sound card configuration example from Frank Barknecht above must finally be entered in a configuration file for modprobe (/lib/modules/modprobe.conf, see man modprobe.conf) so the boot/init process can use it. The process of building the configuration in modprobe.conf differs somewhat from distribution to distribution and, perhaps, also from the 2.4.* to 2.6.* kernels. With Debian GNU/Linux sid/unstable and kernel 2.6.4-rc2 the component configurations to be included in modprobe.conf are found in several files in /etc/modprobe.d:

[email protected]:~$ ls -l /etc/modprobe.d
total 20
-rw-r--r--    1 root     root         5610 2004-01-30 18:04 aliases
lrwxr-xr-x    1 root     root           22 2004-02-02 00:07 alsa -> /etc/alsa/modutils/1.0
drwxr-xr-x    2 root     root         4096 2004-02-23 09:51 arch
-rw-r--r--    1 root     root          363 2003-02-25 06:57 crypto
-rw-r--r--    1 root     root           29 2003-12-20 17:15 nvidia-kernel-nkc

On this Debian system the /etc/modprobe.d/alsa is a symbolic link to /etc/alsa/modutils/1.0 wherein I have entered commands for two cards, as adapted from Frank Barknecht's configuration above:

[email protected]:~$ cat /etc/alsa/modutils/1.0

alias char-major-116 snd
alias char-major-14 soundcore

options snd major=116 cards_limit=4

# Sound card 0 -- PCI adapter: ens1371 
# /lib/modules/2.6.4-rc2/kernel/sound/pci/snd-ens1371.ko

alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-oss
alias sound-service-0-12 snd-pcm-oss
alias /dev/dsp0 snd-pcm-oss

alias snd-card-0 snd-ens1371

alias snd-slot-0 snd-card-0
alias sound-slot-0 snd-slot-0

# Sound card 1 -- VIA motherboard sound chip: via82xx
# /lib/modules/2.6.4-rc2/kernel/sound/pci/snd-via82xx.ko

alias sound-service-1-0 snd-mixer-oss
alias sound-service-1-1 snd-seq-oss
alias sound-service-1-3 snd-pcm-oss
alias sound-service-1-8 snd-seq-oss
alias sound-service-1-12 snd-pcm-oss
alias /dev/dsp1 snd-pcm-oss

alias snd-card-1 snd-via82xx

alias snd-slot-1 snd-card-1
alias sound-slot-1 snd-slot-1

# End /etc/alsa/modutils/1.0

After editing /etc/alsa/modutils/1.0, I then run, on this Debian system, /sbin/update-modules, which updates /lib/modules/modprobe.conf to make it ready for the boot/init process. Other GNU/Linux distributions probably have a similiar utility. The aliases are merged with with all the others as specified in the files in the /etc/modprobe.d/ directory. (Please take a look at /lib/modules/modprobe.conf.)

The kernel must be configured to build ALSA modules and also the modules for your specific sound cards. In this example system the specified modules for the two sound cards are thus:

[email protected]:~$ grep -i "via82xx\|ens1371" /boot/config-2.6.4-rc2
CONFIG_SND_ENS1371=m
CONFIG_SND_VIA82XX=m

After the kernel is installed, these modules are found in /lib/modules/2.6.4-rc2/kernel/sound/pci/:

[email protected]:~$ ls /lib/modules/2.6.4-rc2/kernel/sound/pci/snd* 
/lib/modules/2.6.4-rc2/kernel/sound/pci/snd-ens1371.ko
/lib/modules/2.6.4-rc2/kernel/sound/pci/snd-via82xx.ko

One can see how these modules correspond to the aliases above in /etc/alsa/modutils/1.0.

On a Debian GNU/Linux system the ALSA modules are all loaded from a script, /etc/init.d/alsa, as part of the system initialization. Doing a lsmod will show all the modules loaded on your system.

RE: How do I select one card or the other?

Doing a aplay -l dislays a list of PLAYBACK Hardware Devices. A ~/.asoundrc is useful for (among other things) making handy aliases for each sound card. A simple one could look like the following for this system:

# Start ~/.asoundrc
pcm.ens1371 { type  hw  card 0 }
ctl.ens1371 { type  hw  card 0 }
pcm.via82xx { type  hw  card 1 }
ctl.via82xx { type  hw  card 1 }
# End ~/.asoundrc

Example commands and options for selecting sound cards:

Note options: -d device | device_alias -- Please see man aplay and man alsaplayer for an explanation of the options.

alsaplayer -o alsa -d ens1371  some_k00!.ogg
alsaplayer -o alsa -d hw:0,0  some_k00!.ogg


alsaplayer -o alsa -d via82xx  some_k00!.ogg
alsaplayer -o alsa -d hw:1,0  some_k00!.ogg
aplay -o alsa -Dplug:via82xx  very_r00d.wav


/usr/bin/alsamixer -c 1     # will control card 1 -- the via82xx card.  
/usr/bin/gamix              # or
/usr/bin/gnome-alsamixer    # will provide separate mixer controls for each sound card.


AUDIODEV="via82xx" mySDLapp

These capabilities are the results of the configurations found in /lib/modules/modprobe.conf and ~/.asoundrc.

As an alternative modprobe.conf configuration method, the shell script, /usr/sbin/alsaconf (man alsaconf), may or may not work on your system. If it does, it probably saves a bit of work; otherwise, you now know what to do instead. alsaconf strives to be able to set up sound cards for ALSA on all the varieties of GNU/Linux distributions.

N.B. Please remember that several of the specific examples are for a Debian GNU/Linux sid/unstable system with a 2.6.* kernel. Counterparts to these scripts and configuration files should be found on any GNU/Linux distribution.

Multiple USB Audio Devices

See also: MultipleUSBAudioDevices and Udev

I am using Debian SID and found a very simple solution: I edited the etc/modules document in which the admin can load Modules on boot. First entry is the card you want to be the card 0 and second the Modules for the second card, so you can set the module load order. That's it.

I have all my stuff statically compiled into the kernel

I have all my stuff statically compiled into the kernel, so is there a way to change the order of my cards without using modules?

I found this in mailing list. This was put in linux boot row (in boot loader config file). I do not test this. This should setup via8233 as firs and midi port as second soundcard.

snd-via82xx.index=0 snd-mpu401.index=1 snd-mpu401.port=0x330 snd-mpu401.irq=10

Answer:

OK, thanks, this was easy. For the sake of completeness, here's the relevant part of my menu.lst (grub config file)

title           Debian kernel 2.6.14.3
root            (hd0,0)
kernel          /boot/vmlinuz-2.6.14.3 root=/dev/hda1 ro snd-emu10k1.index=0 snd-intel8x0.index=1
savedefault
boot

I have two cards, a Creative SBLive 5.1 (snd-emu10k1) and a onboard Intel AC97 (snd-intel8x0). With this, the SBLive becomes card0 and the AC97 card1.

For GRUB 2 the command line needs to be included in /etc/default/grub (root privilidges are needed to edit this file). For a Samsung NC10 the following line works:

GRUB_CMDLINE_LINUX="vga=ext snd-hda-intel.index=0 snd-hda-intel.model=samsung-nc10 snd-virmidi.index=1"

Then run update-grub. The syntax seems to be important, note the full stops.

Easy way to do this on Ubuntu Dapper

  1. run sudo nano -w /etc/modprobe.d/alsa-base to edit your alsa config, from a terminal.
  2. change the the appropriate sound-slot-[x] modprobe snd-card-[y] to match your desired order. i.e. if card 0 and card 1 are in reverse order from what you would like, make the following edit:

install sound-slot-0 modprobe snd-card-1
install sound-slot-1 modprobe snd-card-0

Easy way to do this on Ubuntu Edgy

Since the above advice for Ubuntu Dapper didn't work for me this is what I did:

  1. run sudo nano -w /etc/modprobe.d/alsa-base to edit your alsa config, from a terminal.
  2. then I added the following at the end of the file and left the rest intact:

options snd-intel8x0 index=-2
options snd-cs46xx index=-1

Which made the Hercules Fortissimo II (snd-cs46xx) the default sound adapter and also made the onboard NFORCE2 (snd-intel8x0) the secondary sound adapter.

I have a m-audio keystation connected via usb, and it hogs

Question:

I have a m-audio keystation connected via usb, and it hogs, if connected while drivers are loaded via modprobe.conf, card0 regardless of how the index is configured... which isn't bad by itself as aconnect -i only displays

client 16: 'USB Keystation 61es' [type=kernel]
    0 'USB Keystation 61es MIDI 1'

if it's card0. This seems to be a "known" problem... at least I read it somewhere.

The problem I'm facing is that if the keyboard isn't plugged while drivers are loaded, my soundcard switches from card1 to card0, rendering all configuration obsolete.

gentoo modules.conf:

alias snd-card-0 snd-usb-audio
alias snd-card-1 snd-via82xx
alias sound-slot-0 snd-card-0
alias sound-slot-1 snd-card-1

 options snd-via82xx snd_index=1

snd_index=1 or index=1 doesn't make a difference.

linux 2.6.17-gentoo-r4 (alsa 1.0.11rc4)

Suggestion: Try using index=-2, this should solve the problem.

See also

Retrieved from "http://alsa.opensrc.org/MultipleCards"

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