631 lines
18 KiB
Groff
631 lines
18 KiB
Groff
.\"
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.\" Copyright (c) 1998, Luigi Rizzo
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 9, 2009
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.Dt SOUND 4
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.Os
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.Sh NAME
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.Nm sound ,
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.Nm pcm ,
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.Nm snd
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.Nd
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.Fx
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PCM audio device infrastructure
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.Sh SYNOPSIS
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To compile this driver into the kernel, place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device sound"
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.Ed
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.Pp
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Non-PnP sound cards require the following lines in
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.Xr device.hints 5 :
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.Bd -literal -offset indent
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hint.pcm.0.at="isa"
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hint.pcm.0.irq="5"
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hint.pcm.0.drq="1"
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hint.pcm.0.flags="0x0"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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driver provides support for
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.Tn PCM
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audio play and capture.
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This driver also supports various
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.Tn PCI ,
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.Tn ISA ,
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.Tn WSS/MSS
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compatible
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sound cards, AC97 mixer and High Definition Audio.
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Once the
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.Nm
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driver attaches, supported devices provide audio record and
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playback channels.
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The
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.Fx
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sound system provides dynamic mixing
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.Dq VCHAN
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and rate conversion
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.Dq soft formats .
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True full duplex operation is available on most sound cards.
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.Pp
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If the sound card is supported by a bridge driver, the
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.Nm
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driver works in conjunction with the bridge driver.
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.Pp
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Apart from the usual parameters, the flags field is used to specify
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the secondary
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.Tn DMA
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channel (generally used for capture in full duplex cards).
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Flags are set to 0 for cards not using a secondary
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.Tn DMA
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channel, or to 0x10 + C to specify channel C.
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.Pp
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The driver does its best to recognize the installed hardware and drive
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it correctly so the user is not required to add several lines in
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.Pa /boot/device.hints .
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For
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.Tn PCI
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and
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.Tn ISA
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.Tn PnP
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cards this is actually easy
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since they identify themselves.
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For legacy
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.Tn ISA
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cards, the driver looks for
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.Tn MSS
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cards at addresses 0x530 and 0x604 (unless overridden
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in
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.Pa /boot/device.hints ) .
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.Ss Boot Variables
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|
In general, the module
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.Pa snd_foo
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|
corresponds to
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.Cd "device snd_foo"
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|
and can be
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loaded by the boot
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.Xr loader 8
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via
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.Xr loader.conf 5
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|
or from the command line using the
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|
.Xr kldload 8
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utility.
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|
Options which can be specified in
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.Pa /boot/loader.conf
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|
include:
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.Bl -tag -width ".Va snd_emu10k1_load" -offset indent
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.It Va snd_driver_load
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.Pq Dq Li NO
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If set to
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.Dq Li YES ,
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this option loads all available drivers.
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.It Va snd_emu10k1_load
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.Pq Dq Li NO
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If set to
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.Dq Li YES ,
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only the SoundBlaster 5.1 driver and dependent modules will be loaded.
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.It Va snd_foo_load
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.Pq Dq Li NO
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If set to
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.Dq Li YES ,
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load driver for card/chipset foo.
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.El
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.Pp
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To define default values for the different mixer channels,
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set the channel to the preferred value using hints, e.g.:
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.Va hint.pcm.0.line Ns = Ns Qq Li 0 .
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This will mute the input channel per default.
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|
.Ss EQ
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|
The Parametric Software Equlizer (EQ) enables the use of
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.Dq tone
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controls (bass and treble).
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|
Commonly used for ear-candy or frequency compensation due to the vast
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difference in hardware quality.
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EQ is disabled by default, but can be enabled with the
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.Va hint.pcm. Ns Ao Ar X Ac Ns Va .eq
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tunable.
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.Ss VCHANs
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Each device can optionally support more playback and recording channels
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than physical hardware provides by using
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.Dq virtual channels
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or
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.Tn VCHANs .
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.Tn VCHAN
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options can be configured via the
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.Xr sysctl 8
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interface but can only be manipulated while the device is inactive.
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.Ss VPC
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FreeBSD supports independent and individual volume controls for each active
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application, without touching the master
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.Nm
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volume.
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|
This is sometimes referred to as Volume Per Channel (VPC).
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The
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.Tn VPC
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feature is enabled by default.
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.Ss Loader Tunables
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The following loader tunables are used to set driver configuration at the
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.Xr loader 8
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prompt before booting the kernel, or they can be stored in
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.Pa /boot/loader.conf
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in order to automatically set them before booting the kernel.
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|
It is also possible to use
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.Xr kenv 1
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to change these tunables before loading the
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.Nm
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driver.
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The following tunables can not be changed during runtime using
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.Xr sysctl 8 .
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.Bl -tag -width indent
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.It Va hint.pcm. Ns Ao Ar X Ac Ns Va .eq
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Set to 1 or 0 to explicitly enable (1) or disable (0) the equalizer.
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Requires a driver reload if changed.
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Enabling this will make bass and treble controls appear in mixer applications.
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This tunable is undefined by default.
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Equalizing is disabled by default.
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.It Va hint.pcm. Ns Ao Ar X Ac Ns Va .vpc
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Set to 1 or 0 to explicitly enable (1) or disable (0) the
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.Tn VPC
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feature.
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This tunable is undefined by default.
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.Tn VPC
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is however enabled by default.
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.El
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.Ss Runtime Configuration
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There are a number of
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.Xr sysctl 8
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variables available which can be modified during runtime.
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These values can also be stored in
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.Pa /etc/sysctl.conf
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in order to automatically set them during the boot process.
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.Va hw.snd.*
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are global settings and
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.Va dev.pcm.*
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|
are device specific.
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|
.Bl -tag -width indent
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|
.It Va hw.snd.compat_linux_mmap
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|
Linux
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.Xr mmap 2
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|
compability.
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|
The following values are supported (default is 0):
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.Bl -tag -width 2n
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.It -1
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Force disabling/denying PROT_EXEC
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.Xr mmap 2
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requests.
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.It 0
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Auto detect proc/ABI type, allow
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.Xr mmap 2
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for Linux applications, and deny for everything else.
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.It 1
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Always allow PROT_EXEC page mappings.
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.El
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|
.It Va hw.snd.default_auto
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|
Enable to automatically assign default sound unit to the most recent
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attached device.
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|
.It Va hw.snd.default_unit
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|
Default sound card for systems with multiple sound cards.
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|
When using
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|
.Xr devfs 5 ,
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|
the default device for
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.Pa /dev/dsp .
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|
Equivalent to a symlink from
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|
.Pa /dev/dsp
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|
to
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.Pa /dev/dsp Ns Va ${hw.snd.default_unit} .
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|
.It Va hw.snd.feeder_eq_exact_rate
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|
Only certain rates are allowed for precise processing.
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|
The default behavior is however to allow sloppy processing for all rates,
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|
even the unsupported ones.
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|
Enable to toggle this requirement and only allow processing for supported
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|
rates.
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|
.It Va hw.snd.feeder_rate_max
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|
Maximum allowable sample rate.
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|
.It Va hw.snd.feeder_rate_min
|
|
Minimum allowable sample rate.
|
|
.It Va hw.snd.feeder_rate_polyphase_max
|
|
Adjust to set the maximum number of allowed polyphase entries during the
|
|
process of building resampling filters.
|
|
Disabling polyphase resampling has the benefit of reducing memory usage, at
|
|
the expense of slower and lower quality conversion.
|
|
Only applicable when the SINC interpolator is used.
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|
Default value is 183040.
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|
Set to 0 to disable polyphase resampling.
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|
.It Va hw.snd.feeder_rate_quality
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|
Sample rate converter quality.
|
|
Default value is 1, linear interpolation.
|
|
Available options include:
|
|
.Bl -tag -width 2n
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|
.It 0
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|
Zero Order Hold, ZOH.
|
|
Very fast, but with poor quality.
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|
.It 1
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|
Linear interpolation.
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|
Fast, quality is subject to personal preference.
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|
Technically the quality is poor however, due to the lack of anti-aliasing
|
|
filtering.
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|
.It 2
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|
Bandlimited SINC interpolator.
|
|
Implements polyphase banking to boost the conversion speed, at the cost of
|
|
memory usage, with multiple high quality polynomial interpolators to improve
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|
the conversion accuracy.
|
|
100% fixed point, 64bit accumulator with 32bit coefficients and high precision
|
|
sample buffering.
|
|
Quality values are 100dB stopband, 8 taps and 85% bandwidth.
|
|
.It 3
|
|
Continuation of the bandlimited SINC interpolator, with 100dB stopband, 36
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|
taps and 90% bandwidth as quality values.
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|
.It 4
|
|
Continuation of the bandlimited SINC inteprolator, with 100dB stopband, 164
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|
taps and 97% bandwidth as quality values.
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|
.El
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|
.It Va hw.snd.feeder_rate_round
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|
Sample rate rounding threshold, to avoid large prime division at the
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|
cost of accuracy.
|
|
All requested sample rates will be rounded to the nearest threshold value.
|
|
Possible values range between 0 (disabled) and 500.
|
|
Default is 25.
|
|
.It Va hw.snd.latency
|
|
Configure the buffering latency.
|
|
Only affects applications that do not explicitly request
|
|
blocksize / fragments.
|
|
This tunable provides finer granularity than the
|
|
.Va hw.snd.latency_profile
|
|
tunable.
|
|
Possible values range between 0 (lowest latency) and 10 (highest latency).
|
|
.It Va hw.snd.latency_profile
|
|
Define sets of buffering latency conversion tables for the
|
|
.Va hw.snd.latency
|
|
tunable.
|
|
A value of 0 will use a low and aggressive latency profile which can result
|
|
in possible underruns if the application cannot keep up with a rapid irq
|
|
rate, especially during high workload.
|
|
The default value is 1, which is considered a moderate/safe latency profile.
|
|
.It Va hw.snd.maxautovchans
|
|
Global
|
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.Tn VCHAN
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|
setting that only affects devices with at least one playback or recording channel available.
|
|
The sound system will dynamically create up to this many
|
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.Tn VCHANs .
|
|
Set to
|
|
.Dq 0
|
|
if no
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.Tn VCHANS
|
|
are desired.
|
|
Maximum value is 256.
|
|
.It Va hw.snd.report_soft_formats
|
|
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.
|
|
.It Va hw.snd.report_soft_matrix
|
|
Enable seamless channel matrixing even if the hardware does not support it.
|
|
Makes it possible to play multichannel streams even with a simple stereo
|
|
sound card.
|
|
.It Va hw.snd.verbose
|
|
Level of verbosity for the
|
|
.Pa /dev/sndstat
|
|
device.
|
|
Higher values include more output and the highest level,
|
|
four, should be used when reporting problems.
|
|
Other options include:
|
|
.Bl -tag -width 2n
|
|
.It 0
|
|
Installed devices and their allocated bus resources.
|
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.It 1
|
|
The number of playback, record, virtual channels, and
|
|
flags per device.
|
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.It 2
|
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Channel information per device including the channel's
|
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current format, speed, and pseudo device statistics such as
|
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buffer overruns and buffer underruns.
|
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.It 3
|
|
File names and versions of the currently loaded sound modules.
|
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.It 4
|
|
Various messages intended for debugging.
|
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.El
|
|
.It Va hw.snd.vpc_0db
|
|
Default value for
|
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.Nm
|
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volume.
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|
Increase to give more room for attenuation control.
|
|
Decrease for more amplification, with the possible cost of sound clipping.
|
|
.It Va hw.snd.vpc_autoreset
|
|
When a channel is closed the channel volume will be reset to 0db.
|
|
This means that any changes to the volume will be lost.
|
|
Enabling this will preserve the volume, at the cost of possible confusion
|
|
when applications tries to re-open the same device.
|
|
.It Va hw.snd.vpc_mixer_bypass
|
|
The recommended way to use the
|
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.Tn VPC
|
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feature is to teach applications to use
|
|
the correct
|
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.Fn ioctl :
|
|
.Dv SNDCTL_DSP_GETPLAYVOL, SNDCTL_DSP_SETPLAYVOL,
|
|
.Dv SNDCTL_DSP_SETRECVOL, SNDCTL_DSP_SETRECVOL.
|
|
This is however not always possible.
|
|
Enable this to allow applications to use their own existing mixer logic
|
|
to control their own channel volume.
|
|
.It Va hw.snd.vpc_reset
|
|
Enable to restore all channel volumes back to the default value of 0db.
|
|
.It Va dev.pcm.%d.bitperfect
|
|
Enable or disable bitperfect mode.
|
|
When enabled, channels will skip all dsp processing, such as channel
|
|
matrixing, rate converting and equalizing.
|
|
The pure
|
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.Nm
|
|
stream will be fed directly to the hardware.
|
|
If
|
|
.Tn VCHANs
|
|
are enabled, the bitperfect mode will use the
|
|
.Tn VCHAN
|
|
format/rate as the definitive format/rate target.
|
|
The recommended way to use bitperfect mode is to disable
|
|
.Tn VCHANs
|
|
and enable this sysctl.
|
|
Default is disabled.
|
|
.It Va dev.pcm.%d.[play|rec].vchans
|
|
The current number of
|
|
.Tn VCHANs
|
|
allocated per device.
|
|
This can be set to preallocate a certain number of
|
|
.Tn VCHANs .
|
|
Setting this value to
|
|
.Dq 0
|
|
will disable
|
|
.Tn VCHANs
|
|
for this device.
|
|
.It Va dev.pcm.%d.[play|rec].vchanformat
|
|
Format for
|
|
.Tn VCHAN
|
|
mixing.
|
|
All playback paths will be converted to this format before the mixing
|
|
process begins.
|
|
.It Va dev.pcm.%d.[play|rec].vchanmode
|
|
.Tn VCHAN
|
|
format/rate selection.
|
|
Available options include:
|
|
.Bl -tag -width 2n
|
|
.It fixed
|
|
Channel mixing is done using fixed format/rate.
|
|
Advanced operations such as digital passthrough will not work.
|
|
Can be considered as a
|
|
.Dq legacy
|
|
mode.
|
|
This is the default mode for hardware channels which lack support for digital
|
|
formats.
|
|
.It passthrough
|
|
Channel mixing is done using fixed format/rate, but advanced operations such
|
|
as digital passthrough also work.
|
|
All channels will produce sound as usual until a digital format playback is
|
|
requested.
|
|
When this happens all other channels will be muted and the latest incoming
|
|
digital format will be allowed to pass through undisturbed.
|
|
Multiple concurrent digital streams are supported, but the latest stream will
|
|
take precedence and mute all other streams.
|
|
.It adaptive
|
|
Works like the
|
|
.Dq passthrough
|
|
mode, but is a bit smarter, especially for
|
|
multiple
|
|
.Nm
|
|
channels with different format/rate.
|
|
When a new channel is about to start, the entire list of virtual channels will
|
|
be scanned, and the channel with the best format/rate (usually the
|
|
highest/biggest) will be selected.
|
|
This ensures that mixing quality depends on the best channel.
|
|
The downside is that the hardware DMA mode needs to be restarted, which may
|
|
cause annoying pops or clicks.
|
|
.El
|
|
.It Va dev.pcm.%d.[play|rec].vchanrate
|
|
Sample rate speed for
|
|
.Tn VCHAN
|
|
mixing.
|
|
All playback paths will be converted to this sample rate before the mixing
|
|
process begins.
|
|
.It Va dev.pcm.%d.polling
|
|
Experimental polling mode support where the driver operates by querying the
|
|
device state on each tick using a
|
|
.Xr callout 9
|
|
mechanism.
|
|
Disabled by default and currently only available for a few device drivers.
|
|
.El
|
|
.Ss Recording Channels
|
|
On devices that have more than one recording source (ie: mic and line),
|
|
there is a corresponding
|
|
.Pa /dev/dsp%d.r%d
|
|
device.
|
|
.Ss Statistics
|
|
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.
|
|
.Ss IOCTL Support
|
|
The driver supports most of the
|
|
.Tn OSS
|
|
.Fn ioctl
|
|
functions, and most applications work unmodified.
|
|
A few differences exist, while memory mapped playback is
|
|
supported natively and in
|
|
.Tn Linux
|
|
emulation, memory mapped recording is
|
|
not due to
|
|
.Tn VM
|
|
system design.
|
|
As a consequence, some applications may need to be recompiled
|
|
with a slightly modified audio module.
|
|
See
|
|
.In sys/soundcard.h
|
|
for a complete list of the supported
|
|
.Fn ioctl
|
|
functions.
|
|
.Sh FILES
|
|
The
|
|
.Nm
|
|
drivers may create the following
|
|
device nodes:
|
|
.Pp
|
|
.Bl -tag -width ".Pa /dev/audio%d.%d" -compact
|
|
.It Pa /dev/audio%d.%d
|
|
Sparc-compatible audio device.
|
|
.It Pa /dev/dsp%d.%d
|
|
Digitized voice device.
|
|
.It Pa /dev/dspW%d.%d
|
|
Like
|
|
.Pa /dev/dsp ,
|
|
but 16 bits per sample.
|
|
.It Pa /dev/dsp%d.p%d
|
|
Playback channel.
|
|
.It Pa /dev/dsp%d.r%d
|
|
Record channel.
|
|
.It Pa /dev/dsp%d.vp%d
|
|
Virtual playback channel.
|
|
.It Pa /dev/dsp%d.vr%d
|
|
Virtual recording channel.
|
|
.It Pa /dev/sndstat
|
|
Current
|
|
.Nm
|
|
status, including all channels and drivers.
|
|
.El
|
|
.Pp
|
|
The first number in the device node
|
|
represents the unit number of the
|
|
.Nm
|
|
device.
|
|
All
|
|
.Nm
|
|
devices are listed
|
|
in
|
|
.Pa /dev/sndstat .
|
|
Additional messages are sometimes recorded when the
|
|
device is probed and attached, these messages can be viewed with the
|
|
.Xr dmesg 8
|
|
utility.
|
|
.Pp
|
|
The above device nodes are only created on demand through the dynamic
|
|
.Xr devfs 5
|
|
clone handler.
|
|
Users are strongly discouraged to access them directly.
|
|
For specific sound card access, please instead use
|
|
.Pa /dev/dsp
|
|
or
|
|
.Pa /dev/dsp%d .
|
|
.Sh DIAGNOSTICS
|
|
.Bl -diag
|
|
.It pcm%d:play:%d:dsp%d.p%d: play interrupt timeout, channel dead
|
|
The hardware does not generate interrupts to serve incoming (play)
|
|
or outgoing (record) data.
|
|
.It unsupported subdevice XX
|
|
A device node is not created properly.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr snd_ad1816 4 ,
|
|
.Xr snd_als4000 4 ,
|
|
.Xr snd_atiixp 4 ,
|
|
.Xr snd_audiocs 4 ,
|
|
.Xr snd_cmi 4 ,
|
|
.Xr snd_cs4281 4 ,
|
|
.Xr snd_csa 4 ,
|
|
.Xr snd_ds1 4 ,
|
|
.Xr snd_emu10k1 4 ,
|
|
.Xr snd_emu10kx 4 ,
|
|
.Xr snd_envy24 4 ,
|
|
.Xr snd_envy24ht 4 ,
|
|
.Xr snd_es137x 4 ,
|
|
.Xr snd_ess 4 ,
|
|
.Xr snd_fm801 4 ,
|
|
.Xr snd_gusc 4 ,
|
|
.Xr snd_hda 4 ,
|
|
.Xr snd_ich 4 ,
|
|
.Xr snd_maestro 4 ,
|
|
.Xr snd_maestro3 4 ,
|
|
.Xr snd_mss 4 ,
|
|
.Xr snd_neomagic 4 ,
|
|
.Xr snd_sbc 4 ,
|
|
.Xr snd_solo 4 ,
|
|
.Xr snd_spicds 4 ,
|
|
.Xr snd_t4dwave 4 ,
|
|
.Xr snd_uaudio 4 ,
|
|
.Xr snd_via8233 4 ,
|
|
.Xr snd_via82c686 4 ,
|
|
.Xr snd_vibes 4 ,
|
|
.Xr devfs 5 ,
|
|
.Xr device.hints 5 ,
|
|
.Xr loader.conf 5 ,
|
|
.Xr dmesg 8 ,
|
|
.Xr kldload 8 ,
|
|
.Xr sysctl 8
|
|
.Rs
|
|
.%T "Cookbook formulae for audio EQ biquad filter coefficients, by Robert Bristow-Johnson"
|
|
.%O "http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt"
|
|
.Re
|
|
.Rs
|
|
.%T "Julius O'Smith's Digital Audio Resampling"
|
|
.%O "http://ccrma.stanford.edu/~jos/resample/"
|
|
.Re
|
|
.Rs
|
|
.%T "Polynomial Interpolators for High-Quality Resampling of Oversampled Audio, by Olli Niemitalo"
|
|
.%O "http://www.student.oulu.fi/~oniemita/dsp/deip.pdf"
|
|
.Re
|
|
.Rs
|
|
.%T "The OSS API"
|
|
.%O "http://www.opensound.com/pguide/oss.pdf"
|
|
.Re
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
device driver first appeared in
|
|
.Fx 2.2.6
|
|
as
|
|
.Nm pcm ,
|
|
written by
|
|
.An Luigi Rizzo .
|
|
It was later
|
|
rewritten in
|
|
.Fx 4.0
|
|
by
|
|
.An Cameron Grant .
|
|
The API evolved from the VOXWARE
|
|
standard which later became OSS standard.
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
.An Luigi Rizzo Aq luigi@iet.unipi.it
|
|
initially wrote the
|
|
.Nm pcm
|
|
device driver and this manual page.
|
|
.An Cameron Grant Aq gandalf@vilnya.demon.co.uk
|
|
later revised the device driver for
|
|
.Fx 4.0 .
|
|
.An Seigo Tanimura Aq tanimura@r.dl.itc.u-tokyo.ac.jp
|
|
revised this manual page.
|
|
It was then rewritten for
|
|
.Fx 5.2 .
|
|
.Sh BUGS
|
|
Some features of your sound card (e.g., global volume control) might not
|
|
be supported on all devices.
|