JACK is a low-latency audio server, written for any operating system that is reasonably POSIX compliant. It currently exists for Linux, OS X, Solaris, FreeBSD and Windows. 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. 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 no difference in how an application sends or receives data regardless of whether it comes from/goes to 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 jack_client_open() 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. The simple_client.c example demonstrates a complete (simple!) JACK application that just copies the signal arriving at its input port to its output port. Similarly, inprocess.c shows how to write an internal client "plugin" that runs within the JACK server process.
VERSION HISTORY
- Version 0.109.2 posted on 2008-01-30
Several fixes and updates - Version 0.109.2 posted on 2008-01-30
Program Details
- Category: Audio & Multimedia > Other
- Publisher: jackaudio.org/
- License: Free
- Price: N/A
- Version: 1.9.10
- Platform: linux