Audio stream input output
Encyclopedia
Device driver
In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....
protocol for digital audio
Digital audio
Digital audio is sound reproduction using pulse-code modulation and digital signals. Digital audio systems include analog-to-digital conversion , digital-to-analog conversion , digital storage, processing and transmission components...
specified by Steinberg
Steinberg
Steinberg GmbH is a German musical software and equipment company based in Hamburg. It mainly produces music recording, arranging and editing software as used in digital audio workstations and VSTi software synthesizers.- History :...
, providing a low-latency
Latency (audio)
Latency refers to a short period of delay between when an audio signal enters and when it emerges from a system...
and high fidelity interface between a software application and a computer's sound card
Sound card
A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...
. Whereas Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
’s DirectSound
DirectSound
DirectSound is a software component of the Microsoft DirectX library for the Windows operating system. DirectSound provides a low-latency interface to the sound card driver and can handle the mixing and recording of multiple audio streams....
is commonly used as an intermediary signal path for non-professional users, ASIO allows musician
Musician
A musician is an artist who plays a musical instrument. It may or may not be the person's profession. Musicians can be classified by their roles in performing music and writing music.Also....* A person who makes music a profession....
s and sound engineers to access external hardware directly.
Overview
ASIO bypasses the normal audio path from a user application through layers of intermediary Windows operating system software so that an application connects directly to the sound cardSound card
A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...
hardware. Each layer that is bypassed means a reduction in latency (the delay between an application sending audio information and it being reproduced by the sound card, or input signals from the sound card being available to the application). In this way ASIO offers a relatively simple way of accessing multiple audio inputs and outputs independently. Its main strength lies in its method of bypassing the inherently high latency
Latency (engineering)
Latency is a measure of time delay experienced in a system, the precise definition of which depends on the system and the time being measured. Latencies may have different meaning in different contexts.-Packet-switched networks:...
and poor-quality mixing and sample rate conversion
Sample rate conversion
Sample rate conversion is the process of converting a signal from one sampling rate to another, while changing the information carried by the signal as little as possible...
of Windows audio mixing kernels (KMixer), allowing direct, high speed communication with audio hardware. Unlike KMixer, an unmixed ASIO output is "bit identical" or "bit perfect"; that is, the bits sent to or received from the audio interface are identical to those of the original source, thus having higher audio fidelity. In addition, ASIO supports true 24-bit samples, unlike Windows MME and DirectSound which only pass the upper 16 bits. True 24-bit samples offer the potential for a higher signal-to-noise ratio.
Operating systems
Interface support is normally restricted to Microsoft WindowsMicrosoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, since other operating systems (e.g. Apple's Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
and Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
) do not have such mixer latency
Latency (audio)
Latency refers to a short period of delay between when an audio signal enters and when it emerges from a system...
problems (see Core Audio
Core Audio
Core Audio is a low-level API for dealing with sound in Apple's Mac OS X and iOS operating systems. It includes an implementation of the cross-platform OpenAL library....
and ALSA). Starting with Windows Vista
Windows Vista
Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...
, KMixer has been removed and replaced by WASAPI and a new WaveRT port driver. WaveRT cannot provide synchronized audio to multiple devices and does not support external clocks.
As of 2007 there is also an experimental ASIO driver for Wine
Wine (software)
Wine is a free software application that aims to allow computer programs written for Microsoft Windows to run on Unix-like operating systems. Wine also provides a software library, known as Winelib, against which developers can compile Windows applications to help port them to Unix-like...
, a Windows compatibility layer for Linux. This wineasio driver uses the JACK
JACK Audio Connection Kit
JACK is a professional sound server daemon that provides real-time, low latency connections for both audio and MIDI data between applications that implement its API...
sound server as its audio back-end and allows many ASIO-aware applications to run with low-latency under WINE.
Development
- Steinberg's third party developer site, home of the ASIO SDK.
- USBPAL — USB ASIO and third-party WDMWindows Driver ModelIn computing, the Windows Driver Model — also known at one point as the Win32 Driver Model — is a framework for device drivers that was introduced with Windows 98 and Windows 2000 to replace VxD, which was used on older versions of Windows such as Windows 95 and Windows 3.1, as well...
and multi-channel pro audio drivers and hardware DDK. - JuceJuceJUCE is a free software, cross-platform C++ application framework, used for the development of GUI applications and plug-ins.The aim of JUCE is to allow software to be written such that the same source code will compile and run identically on Windows, Mac OS X and Linux platforms...
— an open-source C++ toolkit that includes support for ASIO audio devices. - Portaudio — an open-source C library for audio I/O that includes ASIO support.
- ASIO.NET — Low latency audio using ASIO drivers in Microsoft .NET.
- JAsioHost - Low latency audio using ASIO drivers in JavaJava (programming language)Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
. - wineasio project at SourceForgeSourceForgeSourceForge Enterprise Edition is a collaborative revision control and software development management system. It provides a front-end to a range of software development lifecycle services and integrates with a number of free software / open source software applications .While originally itself...
.
WDM to ASIO drivers
- ASIO4ALL — an independent universal ASIO driver for Windows that brings ASIO support to users of virtually all consumer-grade soundcards and integrated audio chipsets. It also supports semi-pro and pro digital audio systems.
- ASIO2KS — yet another independent universal ASIO driver for Windows. Project appears to have been abandoned.
Utilities and plugins
- ASIOTestSigGen — a simple, audio test signal generator utility to test ASIO setups
- MultiStream ASIO Player — an MP3 player for ASIO with a built-in test signal generator
- J. River Media Center — J. River Media Center natively supports playback where ASIO compliant hardware is present.Winamp plug-in — open-source ASIO output plug-in for WinampWinampWinamp is a media player for Windows-based PCs and Android devices, written by Nullsoft, now a subsidiary of AOL. It is proprietary freeware/shareware, multi-format, extensible with plug-ins and skins, and is noted for its graphical sound visualization, playlist, and media library features.Winamp...
. - XMPlay plug-in — ASIO output plug-in for XMPlay
- foobar2000 plug-in — ASIO output plug-in for foobar2000Foobar2000foobar2000 is a freeware audio player for Windows developed by Peter Pawlowski, a former freelance contractor for Nullsoft. It is known for its highly modular design and extensive SDK which allows third-party developers to do such things as completely replace the interface...
- ASIOWmpPlg plug-in — open-source ASIO output plug-in for Windows Media PlayerWindows Media PlayerWindows Media Player is a media player and media library application developed by Microsoft that is used for playing audio, video and viewing images on personal computers running the Microsoft Windows operating system, as well as on Pocket PC and Windows Mobile-based devices...
and Windows Media CenterWindows Media CenterWindows Media Center is a digital video recorder and media player developed by Microsoft. It is an application that allows users to view and record live television, as well as organize and play music and videos...