Audio Stream Input/Output

ASIO bypasses the normal audio path from a user application through layers of intermediary operating system software, such as KMixer, Direct KS or WASAPI, 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. For this reason, ASIO is sometimes used for Hi-Res Audio playback. Also, the ASIO capable sound cards are widely used for Digital Audio Workstation (DAW) software.

History

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.

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 close to 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.