jack1/doc/mainpage.dox

/*
 * This is the main page of the JACK reference manual, built using
 * doxygen.
 */

/**
@mainpage JACK Audio Connection Kit

@section intro Introduction

JACK is a low-latency audio server, written for POSIX conformant
operating systems such as GNU/Linux and Apple's OS X.  It can connect
several client applications to an audio device, and allow them to
share audio with each other.  Clients can run as separate processes
like normal applications, or within the JACK server as "plugins".

JACK was designed from the ground up for professional audio work, and
its design focuses on two key areas: synchronous execution of all
clients, and low latency operation.

@see <http://jackit.sourceforge.net>


@section jack_overview JACK Overview

Traditionally it has been hard if not impossible to write audio
applications that can share data with each other. In addition,
configuring and managing audio interface hardware has often been one
of the most complex aspect of writing audio software.

JACK changes all this by providing an API that does several things:

    1. provides a high level abstraction for programmers that
       removes the audio interface hardware from the picture and
       allows them to concentrate on the core functionality of
       their software.

    2. allows applications to send and receive audio data to/from
       each other as well as the audio interface. There is
       difference in how an application sends or receives
       data regardless of whether it comes from another application 
       or an audio interface.

For programmers with experience of several other audio APIs such as
PortAudio, Apple's CoreAudio, Steinberg's VST and ASIO as well as many
others, JACK presents a familiar model: your program provides a
"callback" function that will be executed at the right time. Your
callback can send and receive data as well as do other signal
processing tasks. You are not responsible for managing audio
interfaces or threading, and there is no "format negotiation": all
audio data within JACK is represented as 32 bit floating point values.

For those with experiences rooted in the Unix world, JACK presents a
somewhat unfamiliar API. Most Unix APIs are based on the read/write
model spawned by the "everything is a file" abstraction that Unix is
rightly famous for. The problem with this design is that it fails to
take the realtime nature of audio interfaces into account, or more
precisely, it fails to force application developers to pay sufficient
attention to this aspect of their task. In addition, it becomes rather
difficult to facilitate inter-application audio routing when different
programs are not all running synchronously.

Using JACK within your program is very simple, and typically consists
of just:

   - calling @ref jack_client_new to connect to the JACK server.
   - registering "ports" to enable data to be moved to and from
       your application.
   - registering a "process callback" which will be called at the
       right time by the JACK server.
   - telling JACK that your application is ready to start processing
       data.

There is a lot more that you can do with JACK's interfaces, but for
many applications, this is all that is needed. This <simple_client.c>
demonstrates a complete (simple!) JACK application that just copies
the signal arriving at its input port to its output port.

@section reference Reference

The JACK programming interfaces are described in several header files:

  - <jack/jack.h> defines most of the interfaces used by JACK clients.
  - <jack/transport.h> provides a simple transport control mechanism
  for starting, stopping and repositioning clients.  This is described
  in the @ref transport-design document.
  - <jack/types.h> defines most of the data types for JACK.
  - <jack/ringbuffer.h> defines a simple API for using lock-free
  ringbuffers, a very valuable and common data structure in real
  time streaming media software. It is critical for use in
  applications that do disk I/O such as audio file players and
  recording software.

In addition, the example_clients directory provides numerous examples
of simple JACK clients that nevertheless use the API to do something
useful. It includes

  - a metronome.
  - a recording client that can capture any number of channels
      from any JACK sources and store them as an audio file.
  - command line clients to control the transport mechanism,
       change the buffer size and more.      
  - simple examples of wrapping a GUI around a JACK application.
  - tools for checking the status of a running JACK system.

@section license License

Copyright (C) 2001-2003 by Paul Davis and others.

JACK is free software; you can redistribute it and/or modify it under
the terms of the GNU GPL and LGPL licenses as published by the Free
Software Foundation, <http://www.gnu.org>.  The JACK server uses the
GPL, as noted in the source file headers.  However, the JACK library
is licensed under the LGPL, allowing proprietary programs to link with
it and use JACK services.  You should have received a copy of these
Licenses along with the program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
USA.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

*/