JACK stands for JACK Audio Connection Kit. It is a audio server and it has two main features :

  • It allows different audio applications to communicate with each other (for instance, the user can route the output of Pure Data into Ardour to record it),
  • It makes it possible to reduce latency while running Pd by harnessing the real-time capabilities of the operating system.

JACK is just as essential to my setup that my low-latency OS (currently Ubuntu 10.04).

Although JACK is actually just a sound server with no GUI, a very handy user front-end exists. It’s called Qjackctl, and it looks like this :

This interface allows the user to have full control over the JACK server, including :

  • Input and output settings (soundcard…),
  • Audio settings (samplerate, buffer size and latency…),
  • Real-time scheduling.

The user can also control the connections between different audio applications. This can get crazy (JACK is really a very powerful piece of software), though I have never connected more that two apps.

Installing JACK was pretty easy on most Linux distros i’ve tried, though it sometimes required editing a configuration file and adding myself to some groups. I suggest reading the FAQ and the numerous tutorials available on the internet (try this if you’re using Ubuntu).

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3 Responses to JACK

  1. Pingback: Creating a simple delay effect with Pd | Guitar Extended

  2. patrick says:

    Can you described the settings of JACK, more precisely:
    Force 16bits (why)?
    Unlock Memory (why)?
    Priority (why 25)?
    Periods/Buffer (why 2 instead of 3)?


    • Hi Patrick,

      I’ve never changed the default settings (Force 16 bits, Unlock memory, Priority).
      I only change the sample rate to match that of my soundcard, and i try different values for Frames/period and Buffer/period until I get the lowest latency that doesn’t give me X-runs. The picture doesn’t reflect my own settings.

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