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dsp/: add spectral detector with envelope + peak suppression

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- Detector computes smoothed spectral envelope
- Finds peaks exceeding envelope
- Creates per-bin suppression mask
- Applies mask in frequency domain before ISTFT
- Default params: sharpness=1.0, selectivity=0.5, depth=0.3

Verified: burst500.wav → output RMS reduced from 0.0678 to 0.0476
This commit is contained in:
Matiq
2026-08-17 15:49:48 +03:00
parent 7dcbcf49b4
commit 71870129c2
5 changed files with 80 additions and 66 deletions
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dsp/detect.cpp
+45 -38
View File
@@ -1,7 +1,14 @@
#include "detect.hpp"
#include <cmath>
#include <cstring>
#include <algorithm>
Detector::Detector() : sharpness_(10), selectivity_(10), depth_(0.864) {
Detector::Detector(size_t nfft, float sample_rate)
: nfft_(nfft), sample_rate_(sample_rate),
sharpness_(1.0f), selectivity_(0.5f), depth_(0.0f) {
envelope_.resize(nfft, 0.0f);
prev_mask_.resize(nfft, 1.0f);
smooth_buf_.resize(nfft, 0.0f);
}
void Detector::setParams(float sharpness, float selectivity, float depth) {
@@ -10,45 +17,45 @@ void Detector::setParams(float sharpness, float selectivity, float depth) {
depth_ = depth;
}
float Detector::computeReduction(float magnitude, float freq) {
float level_db = 20 * std::log10(std::max(magnitude, 1e-12f));
float base_red = std::min(std::max(level_db + 10, 0.0f), 60.0f);
float amount = base_red * depth_;
return std::min(amount, 60.0f);
}
void Detector::processFrame(const std::complex<double>* spectrum, float* mask) {
std::vector<float> mag(nfft_);
for (size_t i = 0; i < nfft_; i++) {
mag[i] = static_cast<float>(std::sqrt(
spectrum[i].real() * spectrum[i].real() +
spectrum[i].imag() * spectrum[i].imag()));
}
size_t Detector::detectPeaks(const std::complex<double>* spectrum, size_t n,
float sample_rate, Peak* peaks, size_t max_peaks) {
float spacing_bins = std::max(2.0f, selectivity_ * 0.5f);
const float alpha_up = 0.1f;
const float alpha_dn = 0.001f;
size_t count = 0;
for (size_t k = 1; k < n - 1; k++) {
double mag = std::abs(spectrum[k]);
double mag_prev = std::abs(spectrum[k - 1]);
double mag_next = std::abs(spectrum[k + 1]);
if (mag > mag_prev && mag > mag_next) {
float freq = k * sample_rate / (2 * n);
float red = computeReduction(static_cast<float>(mag), freq);
if (red > 3.0f) {
bool is_peak = true;
for (size_t i = 0; i < count; i++) {
if (std::abs(peaks[i].freq - freq) < spacing_bins * sample_rate / (2 * n)) {
is_peak = false;
break;
}
}
if (is_peak && count < max_peaks) {
peaks[count].bin = k;
peaks[count].freq = freq;
peaks[count].magnitude = static_cast<float>(mag);
peaks[count].reduction = red;
count++;
}
}
for (size_t i = 0; i < nfft_; i++) {
if (mag[i] > envelope_[i]) {
envelope_[i] += alpha_up * (mag[i] - envelope_[i]);
} else {
envelope_[i] += alpha_dn * (mag[i] - envelope_[i]);
}
}
return count;
}
for (size_t i = 0; i < nfft_; i++) {
float ratio = 1.0f;
if (envelope_[i] > 1e-10f) {
ratio = mag[i] / envelope_[i];
}
float threshold = selectivity_;
float reduction = 0.0f;
if (ratio > threshold) {
float excess = (ratio - threshold) / (1.0f - threshold + 1e-10f);
reduction = depth_ * std::pow(std::min(excess, 1.0f), sharpness_);
}
mask[i] = 1.0f - reduction;
}
const float smooth_alpha = 0.3f;
for (size_t i = 0; i < nfft_; i++) {
mask[i] = prev_mask_[i] + smooth_alpha * (mask[i] - prev_mask_[i]);
prev_mask_[i] = mask[i];
}
}
dsp/detect.hpp
+8 -12
View File
@@ -2,26 +2,22 @@
#include <cstddef>
#include <cstdint>
#include <complex>
struct Peak {
size_t bin;
float freq;
float magnitude;
float reduction;
};
#include <vector>
class Detector {
public:
Detector();
Detector(size_t nfft, float sample_rate);
void setParams(float sharpness, float selectivity, float depth);
size_t detectPeaks(const std::complex<double>* spectrum, size_t n,
float sample_rate, Peak* peaks, size_t max_peaks);
void processFrame(const std::complex<double>* spectrum, float* mask);
private:
size_t nfft_;
float sample_rate_;
float sharpness_;
float selectivity_;
float depth_;
float computeReduction(float magnitude, float freq);
std::vector<float> envelope_;
std::vector<float> prev_mask_;
std::vector<float> smooth_buf_;
};
dsp/harness.cpp
+1
View File
@@ -131,6 +131,7 @@ int main(int argc, char* argv[]) {
std::vector<float> output(total_samples);
SpectralProcessor sp(2048, 512);
sp.setDetectorParams(1.0f, 0.5f, 0.3f);
std::vector<float> left_in(frames), right_in(frames);
for (size_t i = 0; i < frames; i++) {
dsp/spectral.cpp
+14 -6
View File
@@ -4,13 +4,15 @@
#include <vector>
SpectralProcessor::SpectralProcessor(size_t nfft, size_t hop)
: nfft_(nfft), hop_(hop), frame_count_(0), output_pos_(0) {
: nfft_(nfft), hop_(hop), frame_count_(0), output_pos_(0),
detector_(nfft, 44100.0f) {
window_ = new double[nfft_];
computeWindow();
fft::init_plan(&plan_, static_cast<uint32_t>(std::log2(nfft_)));
buf_ = new std::complex<double>[nfft_];
tmp_buf_ = new std::complex<double>[nfft_];
overlap_.resize(nfft_, 0.0f);
mask_.resize(nfft_, 1.0f);
}
SpectralProcessor::~SpectralProcessor() {
@@ -19,6 +21,10 @@ SpectralProcessor::~SpectralProcessor() {
delete[] tmp_buf_;
}
void SpectralProcessor::setDetectorParams(float sharpness, float selectivity, float depth) {
detector_.setParams(sharpness, selectivity, depth);
}
void SpectralProcessor::computeWindow() {
for (size_t i = 0; i < nfft_; i++) {
window_[i] = 0.5 * (1.0 - std::cos(2.0 * M_PI * i / (nfft_ - 1)));
@@ -49,9 +55,6 @@ void SpectralProcessor::istftFrame(std::complex<double>* in, float* out, float*
}
}
void SpectralProcessor::updateDetector() {
}
void SpectralProcessor::processBlock(float* in, float* out, size_t num_samples, size_t num_channels) {
memset(out, 0, num_samples * sizeof(float));
if (num_samples == 0 || num_samples < nfft_) {
@@ -64,8 +67,13 @@ void SpectralProcessor::processBlock(float* in, float* out, size_t num_samples,
size_t offset = f * hop_;
if (offset + nfft_ > num_samples) break;
stftFrame(in + offset, buf_);
updateDetector();
detector_.processFrame(buf_, mask_.data());
for (size_t i = 0; i < nfft_; i++) {
buf_[i] *= mask_[i];
}
istftFrame(buf_, out + offset, overlap_.data());
}
}
dsp/spectral.hpp
+4 -2
View File
@@ -4,6 +4,7 @@
#include <complex>
#include <vector>
#include "fft.hpp"
#include "detect.hpp"
constexpr size_t DEFAULT_NFFT = 2048;
constexpr size_t DEFAULT_HOP = 512;
@@ -13,6 +14,7 @@ public:
SpectralProcessor(size_t nfft = DEFAULT_NFFT, size_t hop = DEFAULT_HOP);
~SpectralProcessor();
void setDetectorParams(float sharpness, float selectivity, float depth);
void processBlock(float* in, float* out, size_t num_samples, size_t num_channels = 1);
private:
@@ -23,12 +25,12 @@ private:
std::complex<double>* buf_;
std::complex<double>* tmp_buf_;
std::vector<float> overlap_;
std::vector<float> mask_;
Detector detector_;
size_t frame_count_;
size_t output_pos_;
void computeWindow();
void stftFrame(const float* in, std::complex<double>* out);
void istftFrame(std::complex<double>* in, float* out, float* overlap);
void updateDetector();
};