JACK Audio Connection Kit

JACK (JACK Audio Connection Kit) is a professional sound server daemon that provides low-latency audio and MIDI connectivity between applications. Originally developed for Linux by Paul Davis as part of the Ardour DAW project in 2002, JACK has become the standard for professional audio routing on Linux and macOS. Key features: real-time audio routing connecting outputs from one application to inputs of another, enabling complex signal chains and studio-like patching. Ultra-low latency achieved through real-time scheduling (SCHED_FIFO), kernel preempt patches, and frame-accurate synchronization, with typical latencies under 5ms. Multi-client architecture allowing multiple audio applications to share the same audio interface and interconnect via a single sample clock. Sample-accurate synchronization across all connected clients with a global transport control (play, stop, locate) for recording sessions. MIDI support via JACK-MIDI for routing MIDI events between applications alongside audio. Automatic transport synchronization including Bar/Beat/Tick position, SMPTE timecode, and tempo maps for music production. Session management with tools like NSM for saving and restoring entire studio setups. Pipeline-based processing where each application acts as a node in an audio graph (source, effect, sink). Cross-platform on Linux (ALSA, FireWire, OSS), macOS (CoreAudio), and Windows (via JACK2 and PortAudio backend). JACK2 rewrite in C++ with SMP scalability andDBus support. Used by Ardour, Qtractor, Hydrogen, Guitarix, Calf Studio Gear, and the Linux audio ecosystem.