Detectors

Source of truth: the doc comments on each module struct in patches-modules/src/detectors/ define the canonical port names, parameter ranges, and behaviour. This page is kept in sync with those comments.

The detector family converts an audio signal into control events or sustained gates by threshold-crossing the instantaneous signed sample value — not envelope, magnitude, or onset. Two sub-families share a threshold + hysteresis state machine but differ in what they emit:

• Trigger family (AudioToTrigger, PolyAudioToTrigger) emits ADR 0047 sub-sample sync events on a Trigger cable. Intended for clock recovery from oscillator-rate audio, sub-octave division (a divider chain fed by an AudioToTrigger cascade), and driving hard-sync ports from an arbitrary audio source.
• Gate family (AudioToGate, PolyAudioToGate) emits sample- accurate sustained gates (0.0 / 1.0) on a normal mono / poly cable. Intended for sustained-state derivation from a signed-sample stream — the schmitt-trigger pattern.

Onset / transient detection (envelope follower → threshold) is a different problem and not provided here.

AudioToTrigger — Mono threshold-crossing detector

Fires a sub-sample sync event when the input crosses threshold in the chosen direction. The event fraction is the linear-interpolated zero-crossing position inside the current sample interval: frac = (threshold - prev) / (curr - prev), encoded on the output Trigger cable per ADR 0047.

Hysteresis is a two-state machine. After a rising fire the detector disarms; it only re-arms once the signal drops below threshold - hysteresis. Hysteresis controls eligibility, not event location — the fire point is threshold, never threshold - hysteresis. The falling direction is symmetric.

Bidirectional detection tracks the rising and falling arm states independently.

Parameters

Inputs

Outputs

PolyAudioToTrigger — Per-voice threshold-crossing detector

Polyphonic variant. One independent EdgeDetector runs per voice channel, so per-voice transitions fire on the corresponding lane of the output PolyTrigger cable. Parameters apply identically across voices.

Inputs

Outputs

Parameters identical to AudioToTrigger.

AudioToGate — Mono Schmitt-trigger gate

Holds a sustained gate high while signal > threshold; closes the gate when signal < threshold - hysteresis. Values inside the schmitt band hold the previous state. Sample-accurate per ADR 0030 — no sub-sample reporting.

Parameters

Inputs

Outputs

PolyAudioToGate — Per-voice Schmitt-trigger gate

Polyphonic variant. One independent GateSchmitt runs per voice channel, so per-voice gate states are emitted on the lanes of the output poly cable. Parameters apply identically across voices.

Inputs

Outputs

Parameters identical to AudioToGate.

No stereo variants

Neither family has a stereo variant. Both threshold-cross the signed sample value, and there is no consistent collapse of two signed streams into one: (L + R) / 2 cancels antiphase content; max(|L|, |R|) is rectified magnitude (contradicting the mono variants’ signed semantics — a max(|L|, |R|) gate would behave as an envelope-above-threshold detector, a different operation from the mono AudioToGate); and per-channel detection contradicts a single output. A patch needing a stereo-bus gate or trigger derives it from per-channel AudioToTrigger / AudioToGate instances fed by StereoSplitter, or from a dedicated stereo magnitude-summariser (peak / RMS) whose mono output keys an AudioToGate when envelope semantics are wanted. See ADR 0076.