JACK Audio Connection Kit

JACK is a professional sound server daemon that provides real-time low latency connections for both audio and MIDI data between applications that implement its API. The API can be used through either JACK1 or JACK2.

JACK provides a basic infrastructure for audio applications to communicate with each other and with audio hardware. Through JACK, users are enabled to build powerful systems for signal processing and music production. Jack 1 and Jack 2 are equivalent implementations of the same protocol.

JACK2 aka jackdmp is a C++ version of the JACK low-latency audio server for multi-processor machines. It is a new implementation of the JACK server core features that aims at removing some limitations of the JACK1 design. The activation system has been changed for a data flow model and lock-free programming techniques for graph access have been used to have a more dynamic and robust system.

• uses a new client activation model, that allows simultaneous client execution (on a SMP machine) when parallel clients exist in the graph (client that have the same inputs). This activation model allows to better use available CPU on a smp machine, but also works on mono-processor machine.

• uses a lock-free way to access (read/write) the client graph, thus allowing connections/disconnection to be done without interrupting the audio stream. The result is that connections/disconnections are glitch-free. • can work in two different modes at the server level:

• synchronous activation: in a given cycle, the server waits for all clients to be finished (similar to normal jackd)
• asynchronous activation: in a given cycle, the server does not wait for all clients to be finished and use output buffer computed the previous cycle.