Audio Stream Input/Output

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ASIO

Developer(s)	Steinberg
Stable release	1.0.7 / March 18, 2024; 6 months ago (2024-03-18)
Operating system	Microsoft Windows
Platform	x86-64
Included with	WaveLab
Type	API
License	Proprietary
Website	helpcenter.steinberg.de/hc/en-us/articles/17863730844946-Steinberg-built-in-ASIO-Driver-information-download

Audio Stream Input/Output (ASIO) is a computer audio interface driver protocol for digital audio specified by Steinberg, providing high data throughput, synchronization, and low latency between a software application and a computer's audio interface or sound card.^[1]

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 and supports bit resolutions of 16, 24, 32 bit integer and 32 or 64 bit floating point.^[2]

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.^[3]

The latest version ASIO 2.3 introduced monitoring for dropouts in the audio stream.^[4]

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 sound card 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.