7.2 Setting Up the Sound Card

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:

snd_emu10k1_load="YES"

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.

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.

device sound

device pcm

device "snd_emu10k1"

device snd_sbc

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"

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

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: [GIANT-LOCKED]
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 7.2.2.1.

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.

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

7.2.3 Utilizing Multiple Sound Sources

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

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.:

hint.pcm.0.vol="100"

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