Editing Open Sound System

{{Short description|Sound server for Unix-like operating systems}}
{{Infobox software
| name                   = Open Sound System
| logo                   =
| screenshot             =
| caption                =
| collapsible            =
| author                 = Hannu Savolainen
| developer              = [[NCR Corporation]]
| latest release version = 4.2 build 2019
| latest release date    = {{release date and age|2019|03|05}}<ref>{{citation |url=http://ossnext.trueinstruments.com/forum/viewtopic.php?f=19&t=5876 |title=OSS v4.2 build 2019 |access-date=2019-05-10 |archive-date=2022-09-25 |archive-url=https://web.archive.org/web/20220925110149/http://ossnext.trueinstruments.com/forum/viewtopic.php?f=19&t=5876 |url-status=dead }}</ref>
| latest preview version =
| latest preview date    =
| programming language   =
| operating system       = [[Cross-platform]]<ref>{{Cite web|url=http://www.opensound.com/download.cgi|title = OSS Download Registration}}</ref>
| platform               =
| size                   =
| language               =
| genre                  = Audio
| license                = {{ubl|[[BSD License|BSD-2-Clause]]|[[Common Development and Distribution License|CDDL-1.0]]|[[GNU General Public License|GPL-2.0-only]]|[[Proprietary software|Proprietary]] (formerly)}}
| website                = {{URL|http://www.opensound.com/}}
}}

The '''Open Sound System''' (OSS) is an interface for making and capturing sound in [[Unix]] and [[Unix-like]] operating systems.  It is based on standard Unix [[device node|devices]] [[system call]]s (i.e. [[POSIX]] [[read (system call)|read]], [[write (system call)|write]], [[ioctl]], etc.). The term also sometimes refers to the software in a Unix kernel that provides the OSS interface; it can be thought of as a [[device driver]] (or a collection of device drivers) for [[sound card|sound controller]] hardware. The goal of OSS is to allow the writing of sound-based applications that are agnostic of the underlying sound hardware.

OSS was created by [[Hannu Savolainen]] and is distributed under [[Multi-licensing|four license options]], three of which are [[free software licences]], thus making OSS [[free software]].<ref name="OSS-liberated-2007">{{citation|url=http://www.linuxpr.com/releases/9766.html |title=4Front technologies releases the source code for open sound system |publisher=Linux PR |access-date=2012-01-08 |url-status=usurped |archive-url=https://web.archive.org/web/20110725173831/http://www.linuxpr.com/releases/9766.html |archive-date=July 25, 2011 }}</ref>

== API ==
The API is designed to use the traditional Unix framework of open(), read(), write(), and ioctl(), via [[device file]]s. For instance, the default device for sound input and output is '''/dev/dsp'''. Examples using the shell:

 cat [[/dev/random]] > /dev/dsp # plays [[white noise]] through the speaker
 cat /dev/dsp > a.a # reads data from the microphone and copies it to file a.a

OSS implements the [[/dev/audio]] interface. Detailed access to individual sound devices is provided via the {{tt|/dev/oss}} directory. OSS also has MIDI support in {{tt|/dev/sequencer}}, {{tt|/dev/music}} (both legacy) and {{tt|/dev/mini}}.<ref>{{cite web |title=OSS v4.x API reference - OSS API basics |url=http://manuals.opensound.com/developer/ossapi.html |website=manuals.opensound.com}}</ref><ref>{{cite web |title=Open Sound System (3.x) Programmer's Guide |url=http://www.opensound.com/pguide/oss.pdf |access-date=22 February 2023 |date=2000}}</ref>

On Linux, OSS4 is also able to emulate [[Advanced Linux Sound Architecture|ALSA]], its open-source replacement.<ref>{{cite web |title=Tips And Tricks - Open Sound System |url=http://www.opensound.com/wiki/index.php/Tips_And_Tricks#ALSA_Emulation |website=ossnext.trueinstruments.com}}</ref>

== History ==
OSS was originally "VoxWare", a Linux kernel sound driver by Hannu Savolainen. Savolainen made the code available under [[free software]] licenses, GPL for Linux and BSD for BSD distributions. Between November 1993 (and Linux 1.00)<ref>{{Cite web |title=Linux 0.99 patchlevel 14 - Diff - 75bb5836a8a8c0ee44ffd60a51f357b9568f1381^! - pub/scm/linux/kernel/git/nico/archive - Git at Google |url=https://kernel.googlesource.com/pub/scm/linux/kernel/git/nico/archive/+/75bb5836a8a8c0ee44ffd60a51f357b9568f1381%5E!/ |access-date=2024-03-22 |website=kernel.googlesource.com}}</ref> and 1997, OSS was the sole choice of sound system in FreeBSD and Linux. This was changed when Luigi Rizzo wrote a new "pcm" driver for FreeBSD in 1997, and when Jaroslav Kysela started [[Advanced Linux Sound Architecture]] in 1998.<ref name=fbsd>{{cite web |title=Sound - FreeBSD Wiki |url=https://wiki.freebsd.org/Sound |website=wiki.freebsd.org}}</ref>

In 2002, Savolainen was contracted by the company [[4Front Technologies]] and made the upcoming OSS 4, which includes support for newer sound devices and improvements, [[proprietary software|proprietary]]. In response, the Linux community abandoned the OSS/free implementation included in the kernel and development effort switched to the replacement [[Advanced Linux Sound Architecture]] (ALSA). FreeBSD by this time had switched to a "newpcm" project started in 1999 and was not affected.<ref name=fbsd/>

In July 2007, 4Front Technologies released sources for OSS under [[Common Development and Distribution License|CDDL-1.0]] for [[OpenSolaris]] and [[GNU General Public License|GPL-2.0-only]] for [[Linux]]. Drivers for some soundcards remained closed-source and were not included in the release.<ref name="OSS-liberated-2007" /> In January 2008, 4Front Technologies released OSS for [[FreeBSD]] (and other [[BSD]] systems) under the [[BSD Licenses|BSD-2-Clause]].<ref name="OSS-BSD-2008">{{citation |url=http://www.opensound.com/press/2008/oss-bsd.txt |title=4Front Technologies releases OSS for FreeBSD under the BSD license |publisher=opensound.com |access-date=2012-01-08}}</ref>

== Adoption status ==

=== Code ===
OSS4 now exists mostly as a standalone piece of software, not integrated into the kernel source code. The exception is [[Solaris (operating system)|Solaris]] and [[OpenSolaris]], which use a fork of OSS4 called Boomer. It combines the OSS4 framework (audio and mixer) together with Sun's earlier SADA ([[/dev/audio]]) API.<ref>{{citation |url=http://4front-tech.com/hannublog/?page_id=17 |title=Hannu's Blog » Boomer |publisher=4front-tech.com |access-date=2012-01-08 |url-status=dead |archive-url=https://web.archive.org/web/20120316022034/http://4front-tech.com/hannublog/?page_id=17 |archive-date=2012-03-16 }}</ref>

Although Linux distributions such as [[Ubuntu]] made OSS4 available as a software package after it was made free software, they have chosen to ignore any bugs filed against these packages.<ref>{{citation |url=https://help.ubuntu.com/community/OpenSound |title=Ubuntu Documentation: OpenSound |publisher=ubuntu.com |access-date=2012-01-08}}</ref>

=== API ===
The OSS API has remained influential despite the obscurity of the original library. NetBSD's documentation describes it as "the preferred API in FreeBSD and Solaris".<ref name="NetBSDman">{{cite web |title=ossaudio(3) - NetBSD Manual Pages |url=https://man.netbsd.org/NetBSD-10.0-STABLE/ossaudio.3 |website=man.netbsd.org}}</ref>

[[FreeBSD]] contains an independently developed implementation of the OSS API, which includes, among other things, in-kernel resampling, [[Audio mixing (recorded music)|mixing]] (vchans), equalizer, surround sound, and independent volume control for each application. It also supports bit-perfect mode.<ref>{{citation |url=http://www.freebsd.org/cgi/man.cgi?sound |title=sound |publisher=Freebsd.org |date=2009-07-13 |access-date=2012-01-08}}</ref> It gradually evolved from the "newpcm" replacement written in 1999 and caught up with OSS4 API around 2005.<ref name=fbsd/>

[[NetBSD]] supports a compatibility mode for the OSS API, by providing the <code>soundcard.h</code> header file and the <code>libossaudio</code> library, which internally operate using the native Sun-like audio interface. The replacement was first seen in NetBSD 1.3 of 1998.<ref name="NetBSDman"/>

Linux had, as aforementioned, switched to [[Advanced Linux Sound Architecture]] since 2003 (kernel 2.6). ALSA provides an optional, in-kernel, OSS emulation mode that appears to programs as if it were OSS.<ref>{{citation|url=http://www.alsa-project.org/~tiwai/OSS-Emulation.html|title=OSS Emulation|access-date=2012-07-07|archive-url=https://web.archive.org/web/20120605094307/http://www.alsa-project.org/~tiwai/OSS-Emulation.html|archive-date=2012-06-05|url-status=dead}}</ref> ALSA also has a ''aoss'' userspace program that works by intercepting systems calls directed to the OSS device files.<ref>{{cite web |title=aoss(1) — Arch manual pages |url=https://man.archlinux.org/man/extra/alsa-oss/aoss.1.en |website=man.archlinux.org}}</ref>

== OSS/3D ==

OSS/3D is a plugin for music players, which acts as an audio postprocessing engine. Supported players include [[Winamp]], [[Windows Media Player]] (9 or later), musicmatch, [[Sonique (media player)|Sonique]], [[Foobar2000]], [[JetAudio]], [[XMMS]]. It is ported to Windows and Linux platforms. Unlike the OSS, it is [[shareware]].

4Front OSS3D was later renamed to Joesoft Hear.<ref>{{citation |url=http://www.yohng.com/obsolete.html |title=· Obsolete product reference |publisher=Yohng.com |access-date=2012-01-08}}</ref>

== Criticism ==

OSS both as API and as software has been criticized by some developers, such as [[Paul Davis (programmer)|Paul Davis]] (of [[JACK Audio Connection Kit]]) and [[Lennart Poettering]] (of competing [[PulseAudio]]).<ref>{{Cite web|url=http://equalarea.com/paul/alsa-audio.html|title = A tutorial on using the ALSA Audio API}}</ref>{{Failed verification|date=May 2024}}<ref>{{Cite web|url=https://lwn.net/Articles/450299/|title=Interview with Lennart Poettering (LinuxFR.org) [LWN.net]|website=lwn.net}}</ref>

== See also ==
{{Portal|Free and open-source software}}
* [[Advanced Linux Sound Architecture]] – prevailing sound framework in the Linux kernel
* [[PulseAudio]] – a sound server for desktop use, commonly used on Linux systems
* [[JACK Audio Connection Kit]] – prevailing sound server for professional audio production on Linux

== References ==
{{Reflist|30em}}

== External links ==
* {{Official website|http://www.opensound.com/}}
* [http://www.4front-tech.com/wiki/index.php/Building_OSSv4_from_source Building the Open Sound System From Source]
* [http://insanecoding.blogspot.com/2009/06/state-of-sound-in-linux-not-so-sorry.html State of sound in Linux not so sorry after all]

{{Linux kernel}}

[[Category:Application programming interfaces]]
[[Category:Audio libraries]]
[[Category:Cross-platform software]]
[[Category:Free audio software]]
[[Category:Linux kernel features]]
[[Category:Formerly proprietary software]]
[[Category:Formerly open-source or free software]]