Adds the output limiter stage after the 'All' channel. Guarantees the output
never exceeds the ceiling: fixed 1.5 ms look-ahead, stereo-linked sliding-max
peak detection over the look-ahead window -> gain = ceiling/window_max, decoupled
smoothing (fast attack / user release), and a final clamp as the hard guarantee.
- src/dsp/limiter.rs: Limiter (sample-peak; true-peak via oversampling is 4b)
- src/lib.rs: wired as final stage; new globals output_ceiling_db (-24..0) and
limiter_release_ms; latency now the constant three-stage total (bands+All+limiter);
two UI sliders added to the global row
- 14 unit tests (4 new: ceiling guarantee on spikes, loud-sine limiting,
transparency below ceiling, latency)
- README/docs updated (Stage 4 split into 4a done / 4b oversampling)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Investigated the planned global FTZ for the IIR filters and found NIH-plug already
handles it: process_wrapper wraps process()/reset() in a ScopedFtz guard that
enables CPU Flush-To-Zero (x86 MXCSR bit 15 / AArch64 FPCR bit 24, via inline asm,
restored on drop) on the vst3, clap, and standalone paths. SSE is baseline on
x86_64 so FTZ is always active for our build.
So adding our own guard would just duplicate the framework. Instead, removed the
now-redundant flush_denormal() from compressor.rs (the biquads and envelope/RMS
tails already relied on this FTZ) for a single consistent story, and rewrote the
README 'Denormal flushing' note to document that the framework handles it (FTZ,
not DAZ — sufficient for our feed-forward IIR).
No functional change; 10 unit tests still pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Splits the input into low/mid/high with a Linkwitz-Riley 24 dB/oct crossover,
compresses each band, sums them, then runs the sum through a fourth 'All'
compressor. Bypassing the three bands collapses the plugin to a simple full-band
comp driven by 'All' (the crossover sums flat in magnitude).
- src/dsp/biquad.rs: generic RBJ biquad (Transposed Direct Form II), LP/HP/AP
- src/dsp/crossover.rs: 3-band LR4 filterbank; lower band all-pass-compensated at
the higher crossover so the bands sum to flat magnitude (an all-pass, not a
bit-exact null — that only holds for linear-phase FIR). Mirrors nih-plug's
crossover plugin design.
- src/lib.rs: 4 Compressor instances (low/mid/high/all) + Crossover; params
restructured to 4 nested CompressorParams (id_prefix low/mid/high/all) plus
global crossover_low_hz/crossover_high_hz/look_ahead_ms; 4-column lo|mid|hi|all
egui UI; latency = two series stages (bands + all), constant, reported once
- 10 unit tests (adds biquad LP/AP magnitude, crossover flat-magnitude
reconstruction, band-split sanity)
- README: Stage 3 marked done; corrected the 'sum flat' expectation to flat
magnitude (IIR LR sums to an all-pass, not a time-domain null)
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
- Compressor: switchable peak / RMS detection (EnumParam<DetectionMode> in lib.rs
-> use_rms bool in CompressorSettings; DSP stays framework-agnostic). RMS is a
one-pole running mean of the linked squared level with a hardcoded 5 ms window,
updated whenever active so peak<->RMS switching is seamless. New unit test
(RMS compresses a sine less than peak); 6 tests total.
- README: reconciled Implementation Order checklists with actual progress
(Stages 1-2 done; look-ahead/latency + basic UI pulled forward), annotated the
project structure (implemented vs planned), and corrected the Latency and
Denormal-flushing notes to match the code (set_latency_samples once / constant
latency; in-code denormal flush). Overview and goals left unchanged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Implements the single full-band feed-forward compressor (the engine that will be
reused per band + for the 'All' channel). Design follows Giannoulis et al. 2012:
log-domain gain computer with a quadratic soft knee feeding a smooth decoupled
peak detector for attack/release ballistics. Stereo-linked peak detection.
Look-ahead uses a fixed audio delay with a constant reported latency (set once in
initialize); the knob only moves the detector tap within that delay. This avoids
renegotiating latency from process(), which crashed FL Studio when the look-ahead
was adjusted during playback.
- src/dsp/compressor.rs: Compressor + CompressorSettings, RT-safe (no alloc in
process; buffers sized in prepare; envelope denormals flushed in-code)
- src/lib.rs: nested CompressorParams (threshold/ratio/knee/attack/release/makeup/
bypass) + global look-ahead; egui ParamSlider grid; latency reported once
- 5 unit tests (static curve, knee continuity, steady-state convergence, constant
latency); Cargo.toml lib crate-type added so tests link
- README: 'All' channel architecture already documented; look-ahead spec updated
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Mikkeli Matlock