Audio Stream Input/Output (ASIO) is a computer audio interface driver protocol for

digital audio Digital audio is a representation of sound recorded in, or converted into, digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical sampling (signal processing), ...

specified by

Steinberg Steinberg Media Technologies GmbH (trading as Steinberg; ) is a German musical software and hardware company based in Hamburg. It develops software for writing, recording, arranging and editing music, most notably Cubase, Nuendo, and Dorico. It ...

, providing high data throughput, synchronization, and low latency between a software application and a computer's

audio interface An audio interface is a piece of computer hardware that allows the input and output of audio signals to and from a host computer or recording device. Audio interfaces are closely related to computer sound cards, but whereas sound cards are opt ...

sound card A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio ...

. ASIO was initially released in 1997 in order to enable streaming of one or more audio streams from an (multi-input/output) audio interface to a software and vice versa with minimal latency and sample accurate synchronization of the audio streams. It allows the audio streams to use any

sample rate In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or ...

and supports bit resolutions of 16, 24, 32 bit

integer An integer is the number zero (0), a positive natural number (1, 2, 3, ...), or the negation of a positive natural number (−1, −2, −3, ...). The negations or additive inverses of the positive natural numbers are referred to as negative in ...

and 32 or 64 bit

floating point In computing, floating-point arithmetic (FP) is arithmetic on subsets of real numbers formed by a ''significand'' (a signed sequence of a fixed number of digits in some base) multiplied by an integer power of that base. Numbers of this form ...

. The release of ASIO 2.0 in 1999 brought further enhancements such as ASIO Direct Monitoring, where an audio signal is monitored directly from the audio interface with basically zero latency, and ASIO Positioning Protocol, used to sample accurately synchronize a computer to other digital machines such as ADAT recorder or also other computers. ASIO 2.3 introduced monitoring for dropouts in the audio stream. ASIO bypasses the normal audio path from a user application through layers of intermediary operating system software so that an application connects directly to the

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.

Operating systems

Currently only

Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

(AMD/Intel x86-64) is supported by the ASIO SDK. Microsoft announced to incorporate ASIO into their USB Audio Class 2 driver for their Arm64 architecture. While originally supporting MacOS, the introduction of

Core Audio Core Audio is a low-level API for dealing with sound in Apple's macOS and iOS operating systems. It includes an implementation of the cross-platform OpenAL. Apple's Core Audio documentation states that "in creating this new architecture on Ma ...

with macOS X made ASIO support for this OS unnecessary. There is also an experimental ASIO driver for

Wine Wine is an alcoholic drink made from Fermentation in winemaking, fermented fruit. Yeast in winemaking, Yeast consumes the sugar in the fruit and converts it to ethanol and carbon dioxide, releasing heat in the process. Wine is most often made f ...

, WineASIO, for a Windows compatibility layer for Linux. WineASIO driver uses the

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sound server as its audio back-end and allows many ASIO-aware applications to run with low latency under WINE.

Licensing

The license to use the ASIO software development kit (SDK) and to distribute an ASIO driver is free of charge. Yet an SDK license agreement has to be signed. Distribution of the source code is not allowed. For example, the user manual of the Audacity audio editor states: "Licensing restrictions prevent us including ASIO support in released versions of Audacity, but Audacity can be compiled with ASIO support for private, non-distributable use."

References

External links

Steinberg third-party developers support site
where the ASIO SDK can be downloaded {{DEFAULTSORT:Audio Stream Input Output Application programming interfaces Audio libraries Digital audio

Operating systems

Licensing

See also

References

External links