Manual Reference Pages - SOUND (4)
PCM audio device infrastructure
To compile this driver into the kernel, place the following line in your
kernel configuration file:
.Cd device sound
Non-PnP sound cards require the following lines in
Note: There exists some ambiguity in the naming at the moment
(sound, pcm, snd).
It will be resolved soon by renaming
.Cd device sound
.Cd device snd ,
and doing associated changes.
driver provides support for
audio play and capture.
This driver also supports various
sound cards, AC97 mixer and High Definition Audio.
driver attaches, supported devices provide audio record and
sound system provides dynamic mixing
and rate conversion
True full duplex operation is available on most sound cards.
If the sound card is supported by a bridge driver, the
driver works in conjunction with the bridge driver.
Apart from the usual parameters, the flags field is used to specify
channel (generally used for capture in full duplex cards).
Flags are set to 0 for cards not using a secondary
channel, or to 0x10 + C to specify channel C.
The driver does its best to recognize the installed hardware and drive
it correctly so the user is not required to add several lines in
cards this is actually easy
since they identify themselves.
cards, the driver looks for
cards at addresses 0x530 and 0x604 (unless overridden
In general, the module
.Cd device snd_foo
and can be
loaded by the boot
or from the command line using the
Options which can be specified in
If set to
this option loads all available drivers.
If set to
only the SoundBlaster 5.1 driver and dependent modules will be loaded.
If set to
load driver for card/chipset foo.
To define default values for the different mixer channels,
set the channel to the preferred value using hints, e.g.:
This will mute the input channel per default.
Each device can optionally support more playback channels
than physical hardware provides by using
options can be configured via the
interface but can only be manipulated while the device is inactive.
variables are available:
Configure the amount of
bufferspace available for a device.
Set the default block size such that continuous
playback will achieve this
This value can be tuned to improve application performance.
Increase this value when the sound lags and decrease
it if sound stutters or breaks up.
the default device for
Equivalent to a symlink from
Controls the internal format conversion if it is
available transparently to the application software.
When disabled or not available, the application will
only be able to select formats the device natively supports.
Level of verbosity for the
Higher values include more output and the highest level,
three, should be used when reporting problems.
Other options include:
Installed devices and their allocated bus resources.
The number of playback, record, virtual channels, and
flags per device.
Channel information per device including the channels
current format, speed, and pseudo device statistics such as
buffer overruns and buffer underruns.
File names and versions of the currently loaded sound modules.
setting that only affects devices with only one playback channel available.
The sound system will dynamically create up this many
The current number of
allocated per device.
This can be set to preallocate a certain number of
Setting this value to
for this device.
On devices that have more than one recording source (ie: mic and line),
there is a corresponding
Channel statistics are only kept while the device is open.
So with situations involving overruns and underruns, consider the output
while the errant application is open and running.
The driver supports most of the
functions, and most applications work unmodified.
A few differences exist, while memory mapped playback is
supported natively and in
emulation, memory mapped recording is
not due to
As a consequence, some applications may need to be recompiled
with a slightly modified audio module.
for a complete list of the supported
drivers may create the following
Sparc-compatible audio device.
Digitized voice device.
but 16 bits per sample.
Should be connected to a record codec.
status, including all channels and drivers.
The first number in the device node
represents the unit number of the
devices are listed
Additional messages are sometimes recorded when the
device is probed and attached, these messages can be viewed with the
| ac97: dac not ready
AC97 codec is not likely to be accompanied with the sound card.
| unsupported subdevice XX
A device node is not created properly.
The OSS API
device driver first appeared in
.An Luigi Rizzo .
It was later
.An Cameron Grant .
The API evolved from the VOXWARE
standard which later became OSS standard.
.An Luigi Rizzo Aq email@example.com
initially wrote the
device driver and this manual page.
.An Cameron Grant Aq firstname.lastname@example.org
later revised the device driver for
.Fx 4.0 .
.An Seigo Tanimura Aq email@example.com
revised this manual page.
It was then rewritten for
.Fx 5.2 .
Some features of your sound card (e.g., global volume control) might not
be supported on all devices.
|November 26, 2006 ||SOUND (4) || |
Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.