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.\" Copyright (c) 2011-2022 Julien Nadeau Carriere <vedge@csoft.net>
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.Dd December 21, 2022
.Dt AU 3
.Os Agar 1.7
.Sh NAME
.Nm AU
.Nd agar audio interface
.Sh SYNOPSIS
.Bd -literal
#include <agar/au.h>
.Ed
.Sh DESCRIPTION
The Agar-AU library provides a portable interface to audio hardware
and manipulation of digital audio streams.
It aims to accomodate the constraints of real-time audio playback,
as well as the high-quality requirements of offline rendering.
.Pp
The typical usage involves first opening an output audio stream (an
.Xr AU_DevOut 3
object), using
.Xr AU_OpenOut 3 ,
with a specified sample rate and number of output channels (subject to
the limitations of the output device, where applicable).
.Pp
Output devices may also have any number of associated
.Em virtual channels .
.\" each with separate volume levels and effects chains.
.\" Virtual channels may be added or removed at runtime.
.\" Mixing can be performed in different ways, at different quality
.\" levels according to the mixing policy of the output device.
.\" Default mixing policy establishes a one-to-one correspondence between
.\" the virtual channels and the output channels.
.\" If number of virtual vs. output channels differs, the policy can specify
.\" one-to-many or many-to-one correspondences.
.Pp
In a multithreaded application, in order that the
.Nm
library correctly process and mix audio generated from concurrent threads,
virtual channels are further divided into
.Em thread-specific
channels which are automatically created (and may also have their own volume
levels and effects chains).
.Sh INITIALIZATION
.nr nS 1
.Ft "int"
.Fn AU_InitSubsystem "void"
.Pp
.Ft "void"
.Fn AU_DestroySubsystem "void"
.Pp
.nr nS 0
The
.Fn AU_InitSubsystem
function initializes the Agar-AU library.
.Fn AU_DestroySubsystem
releases all resources allocated by Agar-AU.
.Sh SEE ALSO
.Xr AU_DevOut 3 ,
.Xr AU_Wave 3
.Sh HISTORY
The
.Nm
library first appeared in Agar 1.4.2.