Signalsmith-Audio/basics
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Add frequency shifter

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Geraint 2025-07-06 12:53:41 +01:00
parent 2908a8b56f
commit 995339d2a2
9 changed files with 144 additions and 18 deletions
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2
SUPPORT.txt
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@ -1,3 +1,3 @@
# https://geraintluff.github.io/SUPPORT.txt/
2026-01-01 Geraint Luff <geraint@signalsmith-audio.co.uk>
2026-06-01 Geraint Luff <geraint@signalsmith-audio.co.uk>

2
analyser.h
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@ -31,7 +31,7 @@ struct AnalyserSTFX : public BaseEffect {
template<class Storage>
void state(Storage &storage) {
storage.info("[Basics] Analyser", "A Bark-scale spectrum analyser");
storage.info("Analyser", "A Bark-scale spectrum analyser");
storage.version(0);
storage.range("barkResolution", barkResolution)

2
chorus.h
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@ -44,7 +44,7 @@ struct ChorusSTFX : public BaseEffect {
template<class Storage>
void state(Storage &storage) {
storage.info("[Basics] Chorus", "");
storage.info("Chorus", "");
storage.version(0);
stfx::units::rangePercent(storage.range("mix", mix)

17
clap/source/basics.cpp
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@ -6,6 +6,7 @@
#include "signalsmith-basics/analyser.h"
#include "signalsmith-basics/chorus.h"
#include "signalsmith-basics/crunch.h"
#include "signalsmith-basics/freq-shifter.h"
#include "signalsmith-basics/limiter.h"
#include "signalsmith-basics/reverb.h"
@ -25,7 +26,7 @@ bool clap_init(const char *path) {
}, {
CLAP_PLUGIN_FEATURE_ANALYZER,
});
plugins.add<signalsmith::basics::ChorusSTFX>({
.clap_version = CLAP_VERSION,
.id = "uk.co.signalsmith.basics.chorus",
@ -54,6 +55,20 @@ bool clap_init(const char *path) {
CLAP_PLUGIN_FEATURE_DISTORTION,
});
plugins.add<signalsmith::basics::FreqShifterSTFX>({
.clap_version = CLAP_VERSION,
.id = "uk.co.signalsmith.basics.freq-shifter",
.name = "[Basics] Frequency Shifter",
.vendor = "Signalsmith Audio",
.url = "",
.manual_url = "",
.support_url = "",
.version = "1.0.0"
}, {
CLAP_PLUGIN_FEATURE_AUDIO_EFFECT,
CLAP_PLUGIN_FEATURE_FREQUENCY_SHIFTER,
});
plugins.add<signalsmith::basics::LimiterSTFX>({
.clap_version = CLAP_VERSION,
.id = "uk.co.signalsmith.basics.limiter",

7
crunch.h
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@ -1,7 +1,6 @@
/* Copyright 2022 Signalsmith Audio Ltd. / Geraint Luff
See LICENSE.txt and SUPPORT.txt */
#ifndef SIGNALSMITH_BASICS_CRUNCH_H
#define SIGNALSMITH_BASICS_CRUNCH_H
#pragma once
#include "dsp/rates.h"
#include "dsp/filters.h"
@ -40,7 +39,7 @@ struct CrunchSTFX : public BaseEffect {
template<class Storage>
void state(Storage &storage) {
storage.info("[Basics] Crunch", "A simple distortion/saturation");
storage.info("Crunch", "A simple distortion/saturation");
int version = storage.version(0);
if (version != 0) return;
@ -178,5 +177,3 @@ private:
};
}} // namespace
#endif // include guard

118
freq-shifter.h Normal file
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@ -0,0 +1,118 @@
/* Copyright 2022 Signalsmith Audio Ltd. / Geraint Luff
See LICENSE.txt and SUPPORT.txt */
#pragma once
#include "modules/hilbert-iir/hilbert.h"
#include "stfx/stfx-library.h"
#include <cmath>
namespace signalsmith { namespace basics {
template<class BaseEffect>
class FreqShifterSTFX;
using FreqShifterFloat = stfx::LibraryEffect<float, FreqShifterSTFX>;
using FreqShifterDouble = stfx::LibraryEffect<double, FreqShifterSTFX>;
template<class BaseEffect>
struct FreqShifterSTFX : public BaseEffect {
using typename BaseEffect::Sample;
using Complex = std::complex<Sample>;
using typename BaseEffect::ParamRange;
using typename BaseEffect::ParamStepped;
static double unitToShiftHz(double x) {
return 100*x/(1.1 - x*x);
}
static double shiftHzToUnit(double y) {
return (std::sqrt(2500 + 1.1*y*y) - 50)/y;
}
ParamRange mix{1};
ParamRange shift{shiftHzToUnit(50)};
ParamStepped reflect{0};
template<class Storage>
void state(Storage &storage) {
storage.info("Frequency Shifter", "A Hilbert / Bode single-sideband modulator");
int version = storage.version(0);
if (version != 0) return;
stfx::units::rangePercent(storage.range("mix", mix)
.info("mix", "wet/dry")
.range(0, 0.5, 1));
storage.range("shift", shift)
.info("shift", "pre-distortion input gain")
.range(-1, 0, 1)
.unit("Hz", 1, shiftHzToUnit, unitToShiftHz, shiftHzToUnit(-9.99), shiftHzToUnit(9.99))
.unit("Hz", 0, shiftHzToUnit, unitToShiftHz);
storage.stepped("reflect", reflect)
.info("reflect", "0Hz reflection mode")
.range(0, 3)
.label(0, "no reflect/duplicate", "reflect below 0Hz", "duplicate above 0Hz", "always reflect/duplicate");
}
template<class Config>
void configureSTFX(Config &config) {
auto channels = config.outputChannels = config.inputChannels;
config.auxInputs.resize(0);
config.auxOutputs.resize(0);
hilbert = {Sample(config.sampleRate), channels};
}
void reset() {
shiftPhaseBefore = shiftPhaseAfter = 0;
shiftBefore = shiftAfter = 1;
hilbert.reset();
}
template <class Io, class Config, class Block>
void processSTFX(Io &io, Config &config, Block &block) {
auto dry = block.smooth(mix, [](double m){return 1 - m*m;});
auto wet = block.smooth(mix, [](double m){return m*(2 - m);});
auto phaseStep = block.smooth(shift, [&](double u){
auto hz = unitToShiftHz(u);
return hz/config.sampleRate;
});
int mode = reflect;
bool noReflectDown = (mode == 0 || mode == 2);
bool duplicateUp = (mode == 2 || mode == 3);
for (size_t i = 0; i < block.length; ++i) {
auto gainDry = dry.at(i), gainWet = wet.at(i);
for (size_t c = 0; c < config.inputChannels; ++c) {
Sample x = io.input[c][i];
// In general, this may alias at the high end when shifting up
// but our Hilbert has a 20kHz lowpass, so that's enough
// room for our maximum +1000Hz shift
Complex y = shiftAfter*hilbert(x*shiftBefore, c);
io.output[c][i] = gainDry*x + gainWet*y.real();
}
auto ps = phaseStep.at(i);
bool shiftInput = (ps < 0) ? noReflectDown : duplicateUp;
if (shiftInput) {
shiftPhaseBefore += ps;
shiftBefore = std::polar(Sample(1), shiftPhaseBefore*Sample(2*M_PI));
} else {
shiftPhaseAfter += ps;
shiftAfter = std::polar(Sample(1), shiftPhaseAfter*Sample(2*M_PI));
}
}
shiftPhaseBefore -= std::floor(shiftPhaseBefore);
shiftPhaseAfter -= std::floor(shiftPhaseAfter);
}
private:
Sample shiftPhaseBefore = 0, shiftPhaseAfter = 0;
Complex shiftBefore = 1, shiftAfter = 1;
signalsmith::hilbert::HilbertIIR<Sample> hilbert;
};
}} // namespace

1
include/signalsmith-basics/freq-shifter.h Normal file
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@ -0,0 +1 @@
#include "../../freq-shifter.h"

7
limiter.h
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@ -1,7 +1,6 @@
/* Copyright 2022 Signalsmith Audio Ltd. / Geraint Luff
Released under the Boost Software License (see LICENSE.txt) */
#ifndef SIGNALSMITH_BASICS_LIMITER_H
#define SIGNALSMITH_BASICS_LIMITER_H
#pragma once
#include "dsp/delay.h"
#include "dsp/envelopes.h"
@ -36,7 +35,7 @@ struct LimiterSTFX : public BaseEffect {
template<class Storage>
void state(Storage &storage) {
storage.info("[Basics] Limiter", "A simple lookahead limiter");
storage.info("Limiter", "A simple lookahead limiter");
int version = storage.version(4);
if (version != 4) return;
@ -202,5 +201,3 @@ private:
};
}} // namespace
#endif // include guard

6
reverb.h
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@ -1,7 +1,6 @@
/* Copyright 2022 Signalsmith Audio Ltd. / Geraint Luff
Released under the Boost Software License (see LICENSE.txt) */
#ifndef SIGNALSMITH_BASICS_REVERB_H
#define SIGNALSMITH_BASICS_REVERB_H
#pragma once
#include "dsp/delay.h"
#include "dsp/mix.h"
@ -43,7 +42,7 @@ struct ReverbSTFX : public BaseEffect {
template<class Storage>
void state(Storage &storage) {
storage.info("[Basics] Reverb", "An FDN reverb");
storage.info("Reverb", "An FDN reverb");
int version = storage.version(5);
if (version != 5) return;
@ -408,4 +407,3 @@ private:
};
}} // namespace
#endif // include guard