7.2 Setting Up the Sound Card

Contributed by Moses Moore. Enhanced for FreeBSD 5.X by Marc Fonvieille.

7.2.1 Configuring the System

Before you begin, you should know the model of the card you have, the chip it uses, and whether it is a PCI or ISA card. FreeBSD supports a wide variety of both PCI and ISA cards. Check the supported audio devices list of the Hardware Notes to see if your card is supported. This document will also mention which driver supports your card.

To use your sound device, you will need to load the proper device driver. This may be accomplished in one of two ways. The easiest way is to simply load a kernel module for your sound card with kldload(8) which can either be done from the command line:

# kldload snd_emu10k1

or by adding the appropriate line to the file /boot/loader.conf like this:


These examples are for a Creative SoundBlaster® Live! sound card. Other available loadable sound modules are listed in /boot/defaults/loader.conf. If you are not sure which driver to use, you may try to load the snd_driver module:

# kldload snd_driver

This is a metadriver loading the most common device drivers at once. This speeds up the search for the correct driver. It is also possible to load all sound drivers via the /boot/loader.conf facility.

If you wish to find out the driver selected for your soundcard after loading the snd_driver metadriver, you may check the /dev/sndstat file with the cat /dev/sndstat command.

Note: Under FreeBSD 4.X, to load all sound drivers, you have to load the snd module instead of snd_driver.

A second method is to statically compile in support for your sound card in your kernel. The section below provides the information you need to add support for your hardware in this manner. For more information about recompiling your kernel, please see Chapter 8. Configuring a Custom Kernel with Sound Support

The first thing to do is adding the generic audio driver sound(4) to the kernel, for that you will need to add the following line to the kernel configuration file:

device sound

Under FreeBSD 4.X, you would use the following line:

device pcm

Then we have to add the support for our sound card. Therefore, we need to know which driver supports the card. Check the supported audio devices list of the Hardware Notes, to determine the correct driver for your sound card. For example, a Creative SoundBlaster Live! sound card is supported by the snd_emu10k1(4) driver. To add the support for this card, use the following:

device "snd_emu10k1"

Be sure to read the manual page of the driver for the syntax to use. Information regarding the syntax of sound drivers in the kernel configuration can also be found in the /usr/src/sys/conf/NOTES file (/usr/src/sys/i386/conf/LINT for FreeBSD 4.X).

Non-PnP ISA cards may require you to provide the kernel with information on the sound card settings (IRQ, I/O port, etc). This is done via the /boot/device.hints file. At system boot, the loader(8) will read this file and pass the settings to the kernel. For example, an old Creative SoundBlaster 16 ISA non-PnP card will use the snd_sbc(4) driver, with the following line added to the kernel configuration file:

device snd_sbc

as well as the following in /boot/device.hints:


In this case, the card uses the 0x220 I/O port and the IRQ 5.

The syntax used in the /boot/device.hints file is covered in the sound driver manual page. On FreeBSD 4.X, these settings are directly written in the kernel configuration file. In the case of our ISA card, we would only use this line:

device sbc0 at isa? port 0x220 irq 5 drq 1 flags 0x15

The settings shown above are the defaults. In some cases, you may need to change the IRQ or the other settings to match your card. See the snd_sbc(4) manual page for more information.

Note: Under FreeBSD 4.X, some systems with built-in motherboard sound devices may require the following option in the kernel configuration:

options PNPBIOS

7.2.2 Testing the Sound Card

After rebooting with the modified kernel, or after loading the required module, the sound card should appear in your system message buffer (dmesg(8)) as something like:

pcm0: <Intel ICH3 (82801CA)> port 0xdc80-0xdcbf,0xd800-0xd8ff irq 5 at device 31.5 on pci0
pcm0: <Cirrus Logic CS4205 AC97 Codec>

The status of the sound card may be checked via the /dev/sndstat file:

# cat /dev/sndstat
FreeBSD Audio Driver (newpcm)
Installed devices:
pcm0: <Intel ICH3 (82801CA)> at io 0xd800, 0xdc80 irq 5 bufsz 16384
kld snd_ich (1p/2r/0v channels duplex default)

The output from your system may vary. If no pcm devices show up, go back and review what was done earlier. Go through your kernel configuration file again and make sure the correct device is chosen. Common problems are listed in Section

If all goes well, you should now have a functioning sound card. If your CD-ROM or DVD-ROM drive is properly coupled to your sound card, you can put a CD in the drive and play it with cdcontrol(1):

% cdcontrol -f /dev/acd0 play 1

Various applications, such as audio/workman can provide a friendlier interface. You may want to install an application such as audio/mpg123 to listen to MP3 audio files. A quick way to test the card is sending data to the /dev/dsp, like this:

% cat filename > /dev/dsp

where filename can be any file. This command line should produce some noise, confirming the sound card is actually working.

Note: FreeBSD 4.X users need to create the sound card device nodes before being able to use it. If the card showed up in message buffer as pcm0, you will have to run the following as root:

# cd /dev
# sh MAKEDEV snd0

If the card detection returned pcm1, follow the same steps as shown above, replacing snd0 with snd1.

MAKEDEV will create a group of device nodes that will be used by the different sound related applications.

Sound card mixer levels can be changed via the mixer(8) command. More details can be found in the mixer(8) manual page. Common Problems

Error Solution
unsupported subdevice XX

One or more of the device nodes was not created correctly. Repeat the steps above.

sb_dspwr(XX) timed out

The I/O port is not set correctly.

bad irq XX

The IRQ is set incorrectly. Make sure that the set IRQ and the sound IRQ are the same.

xxx: gus pcm not attached, out of memory

There is not enough available memory to use the device.

xxx: can't open /dev/dsp!

Check with fstat | grep dsp if another application is holding the device open. Noteworthy troublemakers are esound and KDE's sound support.

7.2.3 Utilizing Multiple Sound Sources

Contributed by Munish Chopra.

It is often desirable to have multiple sources of sound that are able to play simultaneously, such as when esound or artsd do not support sharing of the sound device with a certain application.

FreeBSD lets you do this through Virtual Sound Channels, which can be set with the sysctl(8) facility. Virtual channels allow you to multiplex your sound card's playback channels by mixing sound in the kernel.

To set the number of virtual channels, there are two sysctl knobs which, if you are the root user, can be set like this:

# sysctl hw.snd.pcm0.vchans=4
# sysctl hw.snd.maxautovchans=4

The above example allocates four virtual channels, which is a practical number for everyday use. hw.snd.pcm0.vchans is the number of virtual channels pcm0 has, and is configurable once a device has been attached. hw.snd.maxautovchans is the number of virtual channels a new audio device is given when it is attached using kldload(8). Since the pcm module can be loaded independently of the hardware drivers, hw.snd.maxautovchans can store how many virtual channels any devices which are attached later will be given.

If you are not using devfs(5), you will have to point your applications at /dev/dsp0.x, where x is 0 to 3 if hw.snd.pcm.0.vchans is set to 4 as in the above example. On a system using devfs(5), the above will automatically be allocated transparently to the user.

7.2.4 Setting Default Values for Mixer Channels

Contributed by Josef El-Rayes.

The default values for the different mixer channels are hardcoded in the sourcecode of the pcm(4) driver. There are a lot of different applications and daemons that allow you to set values for the mixer they remember and set each time they are started, but this is not a clean solution, we want to have default values at the driver level. This is accomplished by defining the appropriate values in /boot/device.hints. E.g.:


This will set the volume channel to a default value of 100, as soon as the pcm(4) module gets loaded.

Note: This is only supported in FreeBSD 5.3-RELEASE and later.

This, and other documents, can be downloaded from ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/.

For questions about FreeBSD, read the documentation before contacting <questions@FreeBSD.org>.
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