Open Sound System: Difference between revisions
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OSS is the only audio API in Linux up through the 2.4 series of official (kernel.org) Linux kernels. ALSA was added starting with 2.5, and in those versions, Linux kernel authors marked OSS as deprecated. 4Front continued to develop OSS outside of the Linux kernel. |
OSS is the only audio API in Linux up through the 2.4 series of official (kernel.org) Linux kernels. ALSA was added starting with 2.5, and in those versions, Linux kernel authors marked OSS as deprecated. 4Front continued to develop OSS outside of the Linux kernel. |
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ALSA provides an optional OSS emulation mode that appears to programs as if it were OSS. Similarly, there was an [http://www.opensound.com/wiki/index.php/Tips_And_Tricks#ALSA_Emulation ALSA emulation] mode in the Linux implementation of OSS. |
ALSA provides an optional OSS emulation mode that appears to programs as if it were OSS. Similarly, there was an [http://www.opensound.com/wiki/index.php/Tips_And_Tricks#ALSA_Emulation ALSA emulation] mode in the Linux implementation of OSS. |
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OSS is better documented than ALSA and its API is much simpler and easier to use.<ref>{{cite web |url=http://insanecoding.blogspot.com/2007/05/sorry-state-of-sound-in-linux.html |title=The Sorry State of Sound in Linux }}</ref> |
OSS is better documented than ALSA and its API is much simpler and easier to use.<ref>{{cite web |url=http://insanecoding.blogspot.com/2007/05/sorry-state-of-sound-in-linux.html |title=The Sorry State of Sound in Linux }}</ref> |
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Revision as of 10:33, 24 April 2011
| Original author(s) | Hannu Savolainen |
|---|---|
| Developer(s) | 4Front Technologies |
| Initial release | 1992 |
| Stable release | 4.2 Build 2004
/ January 6, 2011[1] |
| Operating system | Cross-platform |
| Type | Audio |
| License | BSD License / Common Development and Distribution License / GNU General Public License / Proprietary |
| Website | www.opensound.com |
The Open Sound System (OSS) is an interface for making and capturing sound in Unix or Unix-like operating systems. It is based on standard Unix devices (i.e. POSIX read, 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 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 in 1992 by Hannu Savolainen and is available in 11 major Unix-like operating systems. OSS is distributed under four license options, three of which are free software licences, thus making OSS free software.[2]
API
The API is designed to use the traditional Unix framework of open(), read(), write(), and ioctl(), via special devices. For instance, the default device for sound input and output is /dev/dsp. Examples using the shell:
cat /dev/urandom >/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
Free, proprietary, free
The project was initially free software, but following the project's success, Savolainen was contracted by the company 4Front Technologies and made his support for newer sound devices and improvements proprietary. In response, eventually the Linux community abandoned the OSS/free implementation included in the kernel (an outdated 3.x version, while 4front continued working on 4.x [1]) and development effort switched to the replacement Advanced Linux Sound Architecture (ALSA). Many free software operating systems such as Linux and FreeBSD continued to distribute previous versions of OSS, and continued to maintain and improve these versions.
In July 2007, 4Front Technologies released sources for OSS under CDDL for OpenSolaris and GPL for Linux.[2] In January 2008, 4Front Technologies released OSS for FreeBSD (and other BSD systems) under the BSD License.[3]
OSS in relation to ALSA
In the Linux kernel, there have historically been two uniform sound APIs used. One is OSS; the other is ALSA (Advanced Linux Sound Architecture). ALSA is available for Linux only, and as there is only one implementation of the ALSA interface, ALSA refers equally to that implementation and to the interface itself.
OSS is the only audio API in Linux up through the 2.4 series of official (kernel.org) Linux kernels. ALSA was added starting with 2.5, and in those versions, Linux kernel authors marked OSS as deprecated. 4Front continued to develop OSS outside of the Linux kernel.
ALSA provides an optional OSS emulation mode that appears to programs as if it were OSS. Similarly, there was an ALSA emulation mode in the Linux implementation of OSS.
OSS is better documented than ALSA and its API is much simpler and easier to use.[4]
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, Foobar2000, JetAudio, XMMS. It is ported to Windows and Linux platforms. Unlike the OSS, it is shareware.
Criticism
OSS both as API and as software has been criticized openly and vocally by many free software developers, such as Paul Davis and Lennart Poettering. Often heard arguments against OSS are: the API is practically impossible to virtualize, it lacks support for modern audio features such as timer-based scheduling or proper surround sound support, inability of its developers to work with the Linux kernel community, lack of integration with modern kernel features such as the device model, too low-level interface, as well as general rejection of its design with moving a lot of signal processing code into the kernel.
Most of these criticisms have been addressed in OSS version 4.
Other implementations
FreeBSD contains an independently developed implementation of the OSS API, which includes, among other things, in-kernel resampling, mixing (vchans), equalizer, and independent volume control for each application. It also supports bit-perfect mode.[5]
NetBSD supports a compatibility mode for the OSS API, by providing the soundcard.h header file and the libossaudio library, which internally operate using the native NetBSD Sun-like audio interface.[6]
Solaris and OpenSolaris uses a fork of OSS4 call Boomer. It combines the OSS4 framework (audio and mixer) together with Sun's earlier SADA(/dev/audio) API. [7]
See also
References
- ^ "OSS v4.2 Build 2004". Retrieved 2011-03-05.
- ^ a b "4Front technologies releases the source code for open sound system".
- ^ "4Front Technologies releases OSS for FreeBSD under the BSD license".
- ^ "The Sorry State of Sound in Linux".
- ^ http://www.freebsd.org/cgi/man.cgi?sound
- ^ http://netbsd.gw.com/cgi-bin/man-cgi?ossaudio+3+NetBSD-current
- ^ http://4front-tech.com/hannublog/?page_id=17