148 lines
4.3 KiB
Groff
148 lines
4.3 KiB
Groff
.\" $NetBSD: ossaudio.3,v 1.27 2020/10/20 07:52:04 wiz Exp $
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.\"
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.\" Copyright (c) 1997, 2020 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Lennart Augustsson and Nia Alarie.
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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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd October 20, 2020
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.Dt OSSAUDIO 3
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.Os
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.Sh NAME
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.Nm ossaudio
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.Nd Open Sound System emulation
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.Sh LIBRARY
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.Lb libossaudio
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.Sh SYNOPSIS
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.In soundcard.h
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.Sh DESCRIPTION
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The
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.Nm
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library provides an emulation of the Open Sound System audio interface.
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.Pp
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Use the native
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.Xr audio 4
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and
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.Xr mixer 4
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interfaces for new programs, and this emulation library only for
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building code written for other operating systems.
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.Ss Mixer Control Map
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The following table summarizes the mappings from native interface
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device names to OSSv3 mixer controls.
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.Bl -column ".Sy Native Device Name" "SOUND_MIXER_SPEAKER"
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.It Sy "Native Device Name" Ta Sy "OSS Mixer Control"
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.It *.mic Ta SOUND_MIXER_MIC
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.It *.line Ta SOUND_MIXER_LINE
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.It *.cd Ta SOUND_MIXER_CD
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.It *.dac Ta SOUND_MIXER_PCM
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.It *.aux Ta SOUND_MIXER_LINE1
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.It *.record Ta SOUND_MIXER_IMIX
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.It *.master Ta SOUND_MIXER_VOLUME
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.It *.treble Ta SOUND_MIXER_TREBLE
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.It *.bass Ta SOUND_MIXER_BASS
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.It *.speaker Ta SOUND_MIXER_SPEAKER
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.It *.output Ta SOUND_MIXER_OGAIN
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.It *.input Ta SOUND_MIXER_IGAIN
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.It *.fmsynth Ta SOUND_MIXER_SYNTH
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.It *.midi Ta SOUND_MIXER_SYNTH
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.El
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.Sh COMPATIBILITY
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The
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.Nm
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interface aims to be compatible with the Open Sound System version 4, as
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described in:
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.Pp
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.Rs
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.%A 4Front Technologies
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.%T OSS 4.x Programmer's Guide
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.%U http://manuals.opensound.com/developer/
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.%D 2007
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.Re
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.Sh SEE ALSO
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.Xr ioctl 2 ,
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.Xr audio 4 ,
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.Xr midi 4 ,
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.Xr mixer 4
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.Sh HISTORY
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The
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.Nm
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library first appeared in
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.Nx 1.3 .
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.Pp
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The Open Sound System up to version 3 was originally the preferred
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API for writing audio code under Linux until ALSA became the new default
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in Linux 2.6.
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It remains the preferred API in
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.Fx
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and Solaris, and a large body of code exists supporting it.
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.Sh BUGS
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.Bl -bullet
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.It
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The emulation is incomplete.
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Some less popular features are not emulated (e.g. sync groups), but the
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essential ioctls used by the majority of software are covered.
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.It
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.Nx
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.Dv AUDIO_MIXER_SET
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control types cannot be accurately represented in the OSSv4 mixer API,
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so are treated as enums.
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.It
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Per-stream volume (i.e.
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.Dv SNDCTL_DSP_SETPLAYVOL )
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is not currently implemented as in OSSv4, and will instead modify the
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global volume.
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Applications need to provide samples with the appropriate gain.
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.It
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Linux,
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.Fx ,
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and Solaris provide
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.Pa /dev/dsp
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and
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.Pa /dev/mixer
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devices in place of the
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.Pa /dev/audio
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and
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.Pa /dev/mixer
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devices this compatibility layer must be accessed through on
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.Nx .
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However, changing this is typically trivial when porting programs.
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.It
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The emulation only covers
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.Fn ioctl ,
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there are other differences as well.
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E.g., on a write
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that would block in non-blocking mode Linux returns
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.Dv EINTR
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whereas
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.Nx 1.3
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returns
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.Dv EAGAIN .
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.It
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The emulation uses a #define for
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.Fn ioctl
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so some obscure programs
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can fail to compile.
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.El
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