Apotheosis

The final ascension — a lookahead true-peak brickwall limiter for the master.

Work in progress. Apotheosis is pre-1.0 and under active development. Binaries for macOS and Windows are available from the Releases page (currently unsigned — see the release notes); building from source works too. Expect breaking changes until v1.0.0 ships (see Roadmap).

What it is

Apotheosis is a lookahead brickwall true-peak limiter for the master bus, built on JUCE 8. It is the final gate before export: input gain drives an oversampled true-peak detector, a lookahead delay makes the resulting gain reduction instantaneous (no attack transient) rather than reactive, and a smooth release relaxes it back once the peak has passed. The output's true (inter-sample) peak never exceeds the Ceiling.

Features (v0.2.0 scope)

• Input Gain - -12 to +24 dB trim into the limiter
• Ceiling - -12 to 0 dBTP true-peak target, default -1.0 dBTP (conventional mastering safety margin)
• True-peak detection - 4x oversampled, so inter-sample peaks the naked sample stream would hide are caught and limited, not just sample-domain peaks; per-channel, Stereo Link-weighted (0-100%, default 100% fully max-linked)
• Lookahead - 0.1-20 ms; the mechanism that makes gain-reduction attack instantaneous and click-free rather than a reactive time constant
• Attack - 0-50 ms, default 0 ms; a transient/sustain classifier (not a ramp) - short gain-reduction events recover near-instantly, longer ones follow Release
• Release - 5-1000 ms, log-mapped, how quickly gain reduction relaxes back towards unity
• Auto Release - 0-100%, default 0%; program-dependent modulation of the effective Release time from recent gain-reduction depth
• Release Curve - Exponential / Linear / Smooth, shaping the release phase only (attack always stays instantaneous)
• Clip Mix - 0-100% blend between the transparent limiter path and an alternate tanh soft-clip "clipper" character, both backed by the same never-exceed-ceiling guarantee
• Dither - Off / 16-bit / 24-bit TPDF dither at the output word length, crossed with Dither Shape (Flat / Shaped)
• Metering (engine-side) - gain reduction, output true peak, and Momentary/Short-Term/Integrated LUFS, published via the processor for a future GUI or any host/test harness
• Presets - eight factory presets, user save/load/import/export (single files and zip banks), German-localised preset bar interface
• Full state save/recall via AudioProcessorValueTreeState, with backward-tolerant migration from v0.1's seven-parameter state

Signal flow

Input --> Input Gain --> [4x oversampled] true-peak detect (Stereo Link) --> lookahead min-gain envelope
                                    --> Attack classifier --> Release (curve-shaped, Auto Release-modulated)
                                                                                                       |
     Output <-- Dither (Flat/Shaped) <-- ceiling clamp <-- Clip Mix blend <-- apply gain to lookahead-delayed signal <--+

See docs/manual.md for the full parameter reference and usage tips, and docs/architecture.md for the engineering breakdown, including the lookahead/release mechanism, the latency model, and the internal headroom-margin rationale. New in v0.2.0: research-derived voicing additions sourced in docs/design-brief.md/docs/research-notes.md, and the preset system documented in docs/presets.md.

Roadmap

Milestone	Description	Status
M1	DSP completion & test coverage - Release Curve, Dither, Clip Mix, metering, broadened Catch2 suite	Done
M2	Deep-dive voicing rework (Attack, Auto Release, Stereo Link, Dither Shape) & presets/state recall	Done
M3	Custom GUI & accessibility	Planned
M4	Release engineering - signing, notarization, installers, v1.0.0	Planned

Installation

No pre-built binaries are published yet (see the work-in-progress notice above). Once releases begin, installation will follow the standard plugin locations:

macOS

Format	Path
AU (Component)	~/Library/Audio/Plug-Ins/Components/
VST3	~/Library/Audio/Plug-Ins/VST3/

If Logic Pro doesn't pick up the plugin after installing, force a rescan by resetting the AU cache:

killall -9 AudioComponentRegistrar
auval -a

Windows

Format	Path
VST3	C:\Program Files\Common Files\VST3\

Building from source

Requires JUCE 8.0.14, C++20, and CMake ≥ 3.24. See docs/building.md for full prerequisites and step-by-step build/test commands for macOS and Windows.

cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build
ctest --test-dir build --output-on-failure

License

Apotheosis is licensed under the GNU Affero General Public License v3.0 (AGPLv3).

This project uses JUCE 8, whose open-source tier is licensed under AGPLv3 (as of JUCE 8; JUCE 7 and earlier used GPLv3), which is why this project is AGPLv3 rather than GPLv3. See docs/adr/0002-agplv3-licensing.md for the full reasoning.

VST is a registered trademark of Steinberg Media Technologies GmbH.

Apotheosis is an independent open-source project and is not affiliated with, endorsed by, or sponsored by any plugin manufacturer.