Advanced Linux Sound Architecture ( ALSA ) is a software framework and part of the Linux kernel that provides an application programming interface (API) for sound card device drivers .
18-563: ALSA or alsa can refer to: Advanced Linux Sound Architecture , a Linux kernel component Air Land Sea Application Center , an organization of the United States Department of Defense responsible for developing tactics and procedures Airline Stewardess Association , a trade union ALS Association , an American non-profit organization dealing with amyotrophic lateral sclerosis (ALS) or Lou Gehrig's disease Alsa (bus company) ,
36-414: A backwards-compatibility layer does exist). ALSA has a larger and more complex API than OSS, so it can be more difficult to develop an application that uses ALSA as its sound technology. While ALSA may be configured to provide an OSS emulation layer, such functionality is no longer available or is not installed by default in many Linux distributions. ALSA was designed with some features which were not, at
54-651: A bus company based in Spain Australian Law Students' Association , an Australian law student organisation An alternative name for harees , a Mappila dish in Kerala, south India Alsa (French brand) [ fr ] , a brand of baking and dessert mixes in France Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title ALSA . If an internal link led you here, you may wish to change
72-523: A single address space for all user-mode code. (The kernel-mode code may be in the same address space, or it may be in a second address space). Other operating systems have a per-process address space, with a separate address space for each user-mode process. Another approach taken in experimental operating systems is to have a single address space for all software, and rely on a programming language's semantics to make sure that arbitrary memory cannot be accessed – applications cannot acquire any references to
90-412: Is a physical or logical kernel device capable of input and output. Furthermore, each card may also be addressed by its id , which is an explanatory string such as " Headset " or " ICH 9 ". A card has devices , numbered starting at 0; a device may be of playback type, meaning it outputs sound from the computer, or some other type such as capture , control , timer , or sequencer ; device number 0
108-442: Is achieved in part by using software plug-ins ; for example, many modern sound cards or built-in sound chips do not have a "master volume" control. Instead, for these devices, the user space library provides a software volume control using the " softvol " plug-in, and ordinary application software need not care whether such a control is implemented by underlying hardware or software emulation of such underlying hardware. Additional to
126-437: Is strictly reserved for running a privileged operating system kernel , kernel extensions, and most device drivers . In contrast, user space is the memory area where application software and some drivers execute, typically one address space per process. The term user space (or userland ) refers to all code that runs outside the operating system's kernel. User space usually refers to the various programs and libraries that
144-523: Is used by default when no particular device is specified. A device may have subdevices , numbered starting at 0; a subdevice represents some relevant sound endpoint for the device, such as a speaker pair. If the subdevice is not specified, or if subdevice number −1 is specified, then any available subdevice is used. A card's interface is a description of an ALSA protocol for accessing the card; possible interfaces include: hw , plughw , default , and plug:dmix . The hw interface provides direct access to
162-542: The ALSA names. ALSA API uses ioctl() calls in a way not allowed in the QNX kernel. User-space A modern computer operating system usually uses virtual memory to provide separate address spaces or separate regions of a single address space, called user space and kernel space . Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour. Kernel space
180-476: The ALSA project at its inception were automatic configuration of sound-card hardware and graceful handling of multiple sound devices in a system. ALSA is released under GPL-2.0-or-later and LGPL-2.1-or-later . On Linux, sound servers, like sndio , PulseAudio , JACK (low-latency professional-grade audio editing and mixing) and PipeWire , and higher-level APIs (e.g OpenAL , SDL audio , etc.) work on top of ALSA and its sound card device drivers. ALSA succeeded
198-424: The kernel device, but no software mixing or stream adaptation support. The plughw and default enable sound output where the hw interface would produce an error. An application typically describes sound output by combining all of the aforementioned specifications together in a device string , which has one of the following forms (which are case-sensitive ): An ALSA stream is a data flow representing sound;
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#1732852437103216-663: The kernel to map part of another process's memory space to its own, as is the case for debuggers . Programs can also request shared memory regions with other processes, although other techniques are also available to allow inter-process communication . The most common way of implementing a user mode separate from kernel mode involves operating system protection rings . Protection rings, in turn, are implemented using CPU modes . Typically, kernel space programs run in kernel mode , also called supervisor mode ; normal applications in user space run in user mode. Some operating systems are single address space operating systems —they have
234-400: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=ALSA&oldid=1213042030 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Advanced Linux Sound Architecture Some of the goals of
252-493: The most common stream format is PCM that must be produced in such a way as to match the characteristics or parameters of the hardware, including: The ALSA System on Chip (ASoC) layer aims to provide better support for ALSA on embedded systems that use a system-on-chip (SoC) design. Open Sound System version 4 is able to emulate ALSA. QNX uses a sound system derived from, but not directly compatible with ALSA. The header file and library names are still "asound", same as
270-610: The older Linux port of the Open Sound System (OSS). The project to develop ALSA was led by Jaroslav Kysela, and was based on the Linux device driver for the Gravis Ultrasound sound card. It started in 1998 and was developed separately from the Linux kernel until it was introduced in the 2.5 development series in 2002 (2.5.4–2.5.5). In the 2.6 version, it replaced the previous system, Open Sound System (OSS), by default (although
288-619: The operating system uses to interact with the kernel: software that performs input/output , manipulates file system objects, application software , etc. Each user space process normally runs in its own virtual memory space, and, unless explicitly allowed, cannot access the memory of other processes. This is the basis for memory protection in today's mainstream operating systems, and a building block for privilege separation . A separate user mode can also be used to build efficient virtual machines – see Popek and Goldberg virtualization requirements . With enough privileges, processes can request
306-643: The software framework internal to the Linux kernel, the ALSA project also provides the command-line tools and utilities alsactl , amixer , arecord/aplay and alsamixer , an ncurses -based TUI . There also are GUIs programmed by third-party developers , such as GNOME-ALSAmixer (using GTK ), Kmix, XFCE4-mixer, LXpanel, QasHctl, QasMixer, Pavucontrol, AconnectGUI, tapiir, polarbear, ALSAmixerGUI (using FLTK ), ZynAddSubFX , Yoshimi , and even more. This section provides an overview of basic concepts pertaining to ALSA. Typically, ALSA supports up to eight cards , numbered 0 through 7; each card
324-535: The time of its conception, supported by OSS: Besides the sound device drivers, ALSA bundles a user-space library for application developers who want to use driver features through an interface that is higher-level than the interface provided for direct interaction with the kernel drivers. Unlike the kernel API, which tries to reflect the capabilities of the hardware directly, ALSA's user-space library presents an abstraction that remains as standardized as possible across disparate underlying hardware elements. This goal
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