794 lines
22 KiB
Groff
794 lines
22 KiB
Groff
.\"
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.\" Copyright (c) 2009-2011 Joel Dahl <joel@FreeBSD.org>
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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 January 22, 2012
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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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.Sh DESCRIPTION
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The
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.Nm
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driver is the main component of the
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.Fx
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sound system.
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It works in conjunction with a bridge device driver on supported devices
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and provides PCM audio record and playback once it attaches.
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Each bridge device driver supports a specific set of audio chipsets and
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needs to be enabled together with the
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.Nm
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driver.
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PCI and ISA PnP audio devices identify themselves so users are usually not
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required to add anything to
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.Pa /boot/device.hints .
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.Pp
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Some of the main features of the
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.Nm
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driver are: multichannel audio, per-application
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volume control, dynamic mixing through virtual sound channels, true full
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duplex operation, bit perfect audio, rate conversion and low latency
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modes.
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.Pp
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The
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.Nm
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driver is enabled by default, along with several bridge device drivers.
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Those not enabled by default can be loaded during runtime with
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.Xr kldload 8
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or during boot via
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.Xr loader.conf 5 .
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The following bridge device drivers are available:
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.Pp
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.Bl -bullet -compact
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.It
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.Xr snd_ad1816 4
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.It
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.Xr snd_ai2s 4 (enabled by default on powerpc)
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.It
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.Xr snd_als4000 4
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.It
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.Xr snd_atiixp 4
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.It
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.Xr snd_audiocs 4 (enabled by default on sparc64)
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.It
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.Xr snd_cmi 4
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.It
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.Xr snd_cs4281 4
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.It
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.Xr snd_csa 4
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.It
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.Xr snd_davbus 4 (enabled by default on powerpc)
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.It
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.Xr snd_ds1 4
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.It
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.Xr snd_emu10k1 4
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.It
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.Xr snd_emu10kx 4
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.It
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.Xr snd_envy24 4
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.It
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.Xr snd_envy24ht 4
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.It
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.Xr snd_es137x 4 (enabled by default on amd64, i386, sparc64)
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.It
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.Xr snd_ess 4
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.It
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.Xr snd_fm801 4
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.It
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.Xr snd_gusc 4
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.It
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.Xr snd_hda 4 (enabled by default on amd64, i386)
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.It
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.Xr snd_ich 4 (enabled by default on amd64, i386)
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.It
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.Xr snd_maestro 4
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.It
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.Xr snd_maestro3 4
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.It
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.Xr snd_mss 4
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.It
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.Xr snd_neomagic 4
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.It
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snd_sb16
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.It
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snd_sb8
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.It
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.Xr snd_sbc 4
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.It
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.Xr snd_solo 4
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.It
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.Xr snd_spicds 4
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.It
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.Xr snd_t4dwave 4 (enabled by default on sparc64)
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.It
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.Xr snd_uaudio 4 (enabled by default on amd64, i386, powerpc, sparc64)
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.It
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.Xr snd_via8233 4 (enabled by default on amd64, i386)
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.It
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.Xr snd_via82c686 4
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.It
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.Xr snd_vibes 4
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.El
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.Pp
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Refer to the manual page for each bridge device driver for driver specific
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settings and information.
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.Ss Legacy Hardware
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For old 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
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.Dv 0x530
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and
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.Dv 0x604 .
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These values can be overridden in
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.Pa /boot/device.hints .
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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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.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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.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_driver_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_hda_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 Intel High Definition Audio bridge device driver and dependent
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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 Multichannel Audio
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Multichannel audio, popularly referred to as
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.Dq surround sound
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is supported and enabled by default.
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The FreeBSD multichannel matrix processor supports up to 18 interleaved
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channels, but the limit is currently set to 8 channels (as commonly used
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for 7.1 surround sound).
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The internal matrix mapping can handle reduction, expansion or
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re-routing of channels.
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This provides a base interface for related multichannel
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.Fn ioctl
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support.
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Multichannel audio works both with and without
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.Tn VCHANs .
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.Pp
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Most bridge device drivers are still missing multichannel matrixing
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support, but in most cases this should be trivial to implement.
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Use the
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.Va dev.pcm.%d.[play|rec].vchanformat
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.Xr sysctl(8)
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to adjust the number of channels used.
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The current multichannel interleaved structure and arrangement was
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implemented by inspecting various popular UNIX applications.
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There were no single standard, so much care has been taken to try
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to satisfy each possible scenario, despite the fact that each
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application has its own conflicting standard.
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.Ss EQ
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The Parametric Software Equalizer (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.%d.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.%d.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.%d.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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compatibility.
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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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Automatically assign the default sound unit.
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The following values are supported (default is 1):
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.Bl -tag -width 2n
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.It 0
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Do not assign the default sound unit automatically.
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.It 1
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Use the best available sound device based on playing and recording
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capabilities of the device.
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.It 2
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Use the most recently attached device.
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.El
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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
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Minimum allowable sample rate.
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.It Va hw.snd.feeder_rate_polyphase_max
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Adjust to set the maximum number of allowed polyphase entries during the
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process of building resampling filters.
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Disabling polyphase resampling has the benefit of reducing memory usage, at
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the expense of slower and lower quality conversion.
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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.
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Default value is 1, linear interpolation.
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Available options include:
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.Bl -tag -width 2n
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.It 0
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Zero Order Hold, ZOH.
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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
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filtering.
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.It 2
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Bandlimited SINC interpolator.
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Implements polyphase banking to boost the conversion speed, at the cost of
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memory usage, with multiple high quality polynomial interpolators to improve
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the conversion accuracy.
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100% fixed point, 64bit accumulator with 32bit coefficients and high precision
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sample buffering.
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Quality values are 100dB stopband, 8 taps and 85% bandwidth.
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.It 3
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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
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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.
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All requested sample rates will be rounded to the nearest threshold value.
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Possible values range between 0 (disabled) and 500.
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Default is 25.
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.It Va hw.snd.latency
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Configure the buffering latency.
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Only affects applications that do not explicitly request
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blocksize / fragments.
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This tunable provides finer granularity than the
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.Va hw.snd.latency_profile
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tunable.
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Possible values range between 0 (lowest latency) and 10 (highest latency).
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.It Va hw.snd.latency_profile
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Define sets of buffering latency conversion tables for the
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.Va hw.snd.latency
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tunable.
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A value of 0 will use a low and aggressive latency profile which can result
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in possible underruns if the application cannot keep up with a rapid irq
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rate, especially during high workload.
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The default value is 1, which is considered a moderate/safe latency profile.
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.It Va hw.snd.maxautovchans
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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.
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The sound system will dynamically create up to this many
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.Tn VCHANs .
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Set to
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.Dq 0
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if no
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.Tn VCHANs
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are desired.
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Maximum value is 256.
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.It Va hw.snd.report_soft_formats
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Controls the internal format conversion if it is
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available transparently to the application software.
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When disabled or not available, the application will
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only be able to select formats the device natively supports.
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.It Va hw.snd.report_soft_matrix
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Enable seamless channel matrixing even if the hardware does not support it.
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Makes it possible to play multichannel streams even with a simple stereo
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sound card.
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.It Va hw.snd.verbose
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Level of verbosity for the
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.Pa /dev/sndstat
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device.
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Higher values include more output and the highest level,
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four, should be used when reporting problems.
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Other options include:
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.Bl -tag -width 2n
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.It 0
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Installed devices and their allocated bus resources.
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.It 1
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The number of playback, record, virtual channels, and
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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
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File names and versions of the currently loaded sound modules.
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.It 4
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Various messages intended for debugging.
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.El
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.It Va hw.snd.vpc_0db
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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.
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Decrease for more amplification, with the possible cost of sound clipping.
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.It Va hw.snd.vpc_autoreset
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When a channel is closed the channel volume will be reset to 0db.
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This means that any changes to the volume will be lost.
|
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Enabling this will preserve the volume, at the cost of possible confusion
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when applications tries to re-open the same device.
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.It Va hw.snd.vpc_mixer_bypass
|
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The recommended way to use the
|
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.Tn VPC
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feature is to teach applications to use
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the correct
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.Fn ioctl :
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.Dv SNDCTL_DSP_GETPLAYVOL, SNDCTL_DSP_SETPLAYVOL,
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.Dv SNDCTL_DSP_SETRECVOL, SNDCTL_DSP_SETRECVOL.
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This is however not always possible.
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Enable this to allow applications to use their own existing mixer logic
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to control their own channel volume.
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.It Va hw.snd.vpc_reset
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Enable to restore all channel volumes back to the default value of 0db.
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.It Va dev.pcm.%d.bitperfect
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Enable or disable bitperfect mode.
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When enabled, channels will skip all dsp processing, such as channel
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matrixing, rate converting and equalizing.
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The pure
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.Nm
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stream will be fed directly to the hardware.
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If
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.Tn VCHANs
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are enabled, the bitperfect mode will use the
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.Tn VCHAN
|
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format/rate as the definitive format/rate target.
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The recommended way to use bitperfect mode is to disable
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.Tn VCHANs
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and enable this sysctl.
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Default is disabled.
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.It Va dev.pcm.%d.[play|rec].vchans
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The current number of
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.Tn VCHANs
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allocated per device.
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|
This can be set to preallocate a certain number of
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.Tn VCHANs .
|
|
Setting this value to
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.Dq 0
|
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will disable
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.Tn VCHANs
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for this device.
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.It Va dev.pcm.%d.[play|rec].vchanformat
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Format for
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.Tn VCHAN
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mixing.
|
|
All playback paths will be converted to this format before the mixing
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process begins.
|
|
By default only 2 channels are enabled.
|
|
Available options include:
|
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.Bl -tag -width 2n
|
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.It s16le:1.0
|
|
Mono
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.It s16le:2.0
|
|
Stereo, 2 channels (left, right).
|
|
.It s16le:2.1
|
|
3 channels (left, right, LFE).
|
|
.It s16le:3.0
|
|
3 channels (left, right, rear center).
|
|
.It s16le:4.0
|
|
Quadraphonic, 4 channels (front/rear left and right).
|
|
.It s16le:4.1
|
|
5 channels (4.0 + LFE).
|
|
.It s16le:5.0
|
|
5 channels (4.0 + center).
|
|
.It s16le:5.1
|
|
6 channels (4.0 + center + LFE).
|
|
.It s16le:6.0
|
|
6 channels (4.0 + front/rear center).
|
|
.It s16le:6.1
|
|
7 channels (6.0 + LFE).
|
|
.It s16le:7.1
|
|
8 channels (4.0 + center + LFE + left and right side).
|
|
.El
|
|
.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.
|
|
The
|
|
.Xr mixer 8
|
|
utility can be used to start and stop recording from an specific 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 EXAMPLES
|
|
Use the sound metadriver to load all
|
|
.Nm
|
|
bridge device drivers at once
|
|
(for example if it is unclear which the correct driver to use is):
|
|
.Pp
|
|
.Dl kldload snd_driver
|
|
.Pp
|
|
Load a specific bridge device driver, in this case the Intel
|
|
High Definition Audio driver:
|
|
.Pp
|
|
.Dl kldload snd_hda
|
|
.Pp
|
|
Check the status of all detected
|
|
.Nm
|
|
devices:
|
|
.Pp
|
|
.Dl cat /dev/sndstat
|
|
.Pp
|
|
Change the default sound device, in this case to the second device.
|
|
This is handy if there are multiple
|
|
.Nm
|
|
devices available:
|
|
.Pp
|
|
.Dl sysctl hw.snd.default_unit=1
|
|
.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_ai2s 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_davbus 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 mixer 8 ,
|
|
.Xr sysctl 8
|
|
.Rs
|
|
.%T "Cookbook formulae for audio EQ biquad filter coefficients, by Robert Bristow-Johnson"
|
|
.%U "http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt"
|
|
.Re
|
|
.Rs
|
|
.%T "Julius O'Smith's Digital Audio Resampling"
|
|
.%U "http://ccrma.stanford.edu/~jos/resample/"
|
|
.Re
|
|
.Rs
|
|
.%T "Polynomial Interpolators for High-Quality Resampling of Oversampled Audio, by Olli Niemitalo"
|
|
.%U "http://www.student.oulu.fi/~oniemita/dsp/deip.pdf"
|
|
.Re
|
|
.Rs
|
|
.%T "The OSS API"
|
|
.%U "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.
|