8.2. Setting Up the Sound Card

Contributed by Moses Moore.
Enhanced by Marc Fonvieille.

8.2.1. Configuring the System

Before beginning the configuration, determine the model of the sound card and the chip it uses. FreeBSD supports a wide variety of sound cards. Check the supported audio devices list of the Hardware Notes to see if the card is supported and which FreeBSD driver it uses.

In order to use the sound device, the proper device driver must be loaded. This may be accomplished in one of two ways. The easiest way is to load a kernel module for the sound card with kldload(8). This example loads the driver for a Creative SoundBlaster® Live! sound card:

# kldload snd_emu10k1

To automate the loading of this driver at boot time, add the driver to /boot/loader.conf. The line for this driver is:


Other available sound modules are listed in /boot/defaults/loader.conf. When unsure which driver to use, load the snd_driver module:

# kldload snd_driver

This is a metadriver which loads all of the most common sound drivers and can be used to speed up the search for the correct driver. It is also possible to load all sound drivers by adding the metadriver to /boot/loader.conf.

To determine which driver was selected for the sound card after loading the snd_driver metadriver, type cat /dev/sndstat.

Users who prefer to statically compile in support for the sound card in a custom kernel should refer to the instructions in the next section. For more information about recompiling a kernel, refer to Chapter 9, Configuring the FreeBSD Kernel. Configuring a Custom Kernel with Sound Support

When using a custom kernel to provide sound support, make sure that the audio framework driver exists in the custom kernel configuration file:

device sound

Next, add support for the sound card. Therefore, you need to know which driver supports the card. To continue the example of the Creative SoundBlaster® Live! sound card from the previous section, use the following line in the custom kernel configuration file:

device snd_emu10k1

Be sure to read the manual page of the driver for the syntax to use. The explicit syntax for the kernel configuration of every supported sound driver can also be found in /usr/src/sys/conf/NOTES.

Non-PnP ISA sound cards may require the IRQ and I/O port settings of the card to be added to /boot/device.hints. During the boot process, loader(8) reads this file and passes the settings to the kernel. For example, an old Creative SoundBlaster® 16 ISA non-PnP card will use the snd_sbc(4) driver in conjunction with snd_sb16. For this card, the following lines must be added to the kernel configuration file:

device snd_sbc device snd_sb16

If the card uses the 0x220 I/O port and IRQ 5, these lines must also be added to /boot/device.hints:

hint.sbc.0.at="isa" hint.sbc.0.port="0x220" hint.sbc.0.irq="5" hint.sbc.0.drq="1" hint.sbc.0.flags="0x15"

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

The syntax used in /boot/device.hints is described in sound(4) and the manual page for the driver of the sound card.

The settings shown above are the defaults. In some cases, the IRQ or other settings may need to be changed to match the card. Refer to snd_sbc(4) for more information about this card.

8.2.2. Testing the Sound Card

After rebooting into the custom kernel, or after loading the required module, the sound card should appear in the system message buffer. Run dmesg(8) and look for a message like:

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

The status of the sound card may also be checked using this command:

# 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 may vary between systems. If no pcm devices are listed, go back and review the kernel configuration file and make sure the correct device driver was chosen. Common problems are listed in Section, “Common Problems”.

If all goes well, the sound card should now work in os;. If the CD-ROM or DVD-ROM drive's audio-out pins are properly connected to the sound card, one can insert an audio CD in the drive and play it with cdcontrol(1):

% cdcontrol -f /dev/acd0 play 1

Various applications, such as audio/workman provide a friendlier interface. The audio/mpg123 port can be installed to listen to MP3 audio files.

Another quick way to test the card is to send data to /dev/dsp:

% cat filename > /dev/dsp

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


The /dev/dsp* device nodes will be created automatically as needed. When not in use, they do not exist and will not appear in the output of ls(1).

Sound card mixer levels can be changed using mixer(8). More details can be found in mixer(8). Common Problems

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.

Another issue is that modern graphics cards often come with their own sound driver, for use with HDMI and similar. This sound device will sometimes be enumerated before the sound card and the sound card will subsequently not be used as the default playback device. To check if this is the case, run dmesg and look for pcm. The output looks something like this:

... hdac0: HDA Driver Revision: 20100226_0142 hdac1: HDA Driver Revision: 20100226_0142 hdac0: HDA Codec #0: NVidia (Unknown) hdac0: HDA Codec #1: NVidia (Unknown) hdac0: HDA Codec #2: NVidia (Unknown) hdac0: HDA Codec #3: NVidia (Unknown) pcm0: <HDA NVidia (Unknown) PCM #0 DisplayPort> at cad 0 nid 1 on hdac0 pcm1: <HDA NVidia (Unknown) PCM #0 DisplayPort> at cad 1 nid 1 on hdac0 pcm2: <HDA NVidia (Unknown) PCM #0 DisplayPort> at cad 2 nid 1 on hdac0 pcm3: <HDA NVidia (Unknown) PCM #0 DisplayPort> at cad 3 nid 1 on hdac0 hdac1: HDA Codec #2: Realtek ALC889 pcm4: <HDA Realtek ALC889 PCM #0 Analog> at cad 2 nid 1 on hdac1 pcm5: <HDA Realtek ALC889 PCM #1 Analog> at cad 2 nid 1 on hdac1 pcm6: <HDA Realtek ALC889 PCM #2 Digital> at cad 2 nid 1 on hdac1 pcm7: <HDA Realtek ALC889 PCM #3 Digital> at cad 2 nid 1 on hdac1 ...

Here the graphics card (NVidia) has been enumerated before the sound card (Realtek ALC889). To use the sound card as the default playback device, change hw.snd.default_unit to the unit that should be used for playback:

# sysctl hw.snd.default_unit=n

Here, n is the number of the sound device to use. In this example, it should be 4. Make this change permanent by adding the following line to /etc/sysctl.conf:


8.2.3. Utilizing Multiple Sound Sources

Contributed by Munish Chopra.

It is often desirable to have multiple sources of sound that are able to play simultaneously. FreeBSD uses Virtual Sound Channels, which can be enabled using sysctl(8). Virtual channels allow one to multiplex the sound card's playback by mixing sound in the kernel.

To set the number of virtual channels, three sysctl(8) knobs are available:

# sysctl dev.pcm.0.play.vchans=4 # sysctl dev.pcm.0.rec.vchans=4 # sysctl hw.snd.maxautovchans=4

The above example allocates four virtual channels, which is a practical number for everyday use. Both dev.pcm.0.play.vchans=4 and dev.pcm.0.rec.vchans=4 are the number of virtual channels pcm0 has for playback and recording, and are configurable after 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 indicates how many virtual channels will be given to devices when they are attached. Refer to pcm(4) for more information.


The number of virtual channels for a device cannot be changed while it is in use. First, close any programs using the device, such as music players or sound daemons.

The correct pcm device will automatically be allocated transparently to a program that requests /dev/dsp0.

8.2.4. Setting Default Values for Mixer Channels

Contributed by Josef El-Rayes.

The default values for the different mixer channels are hardcoded in the source code of the pcm(4) driver. There are many different applications and daemons that allow values to be set for the mixer that are remembered between invocations, but this is not a clean solution. It is possible to set default mixer values at the driver level. This is accomplished by defining the appropriate values in /boot/device.hints, as seen in this example:


This will set the volume channel to a default value of 50 when the pcm(4) module is loaded.

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