truce-au

Audio Unit v2 + v3 format wrapper for the truce audio plugin framework.

Overview

Bridges a truce PluginExport implementation to Apple's Audio Unit API. The same Rust dylib serves both AU v2 (.component, in-process) and AU v3 (.appex inside a container .app, sandboxed) - only the bundle shape and the surrounding shim differ. The framework dylib is the identical artifact in either case; cargo-truce's install / package commands wrap it in the right bundle layout.

This crate only builds on macOS. User plugins opt into AU by adding truce-au = { workspace = true, optional = true } and gating it behind an au Cargo feature.

What it handles

• AudioComponent (v2) and AUAudioUnit (v3) registration
• Audio render block bridging + sample-rate / block-size lifecycle
• Parameter tree construction from truce parameter metadata
• Plugin state serialization via truce_core::state
• GUI view hosting via NSViewController (v2) / AUViewController (v3)
• Effects (aufx), instruments (aumu), and MIDI processors (aumi)

Architecture

• v2 uses a hand-written C shim (shim/au_v2_shim.c) that exposes an AudioComponentFactory to the host and forwards every callback into Rust via a C ABI function-pointer table.
• v3 uses a Swift AUAudioUnit subclass generated at install time by cargo truce (so it can stamp in plugin-specific identifiers), with the same Rust-side callback table.

AU type codes (aufx / aumu / aumi) are derived from the plugin's category in truce.toml by truce::plugin_info!() at compile time.

Part of truce. Docs.