move to new cspot

components/spotify/cspot/bell/main/audio-dsp/Compressor.cpp

@@ -0,0 +1,88 @@
+#include "Compressor.h"
+
+using namespace bell;
+
+float log2f_approx(float X) {
+  float Y, F;
+  int E;
+  F = frexpf(fabsf(X), &E);
+  Y = 1.23149591368684f;
+  Y *= F;
+  Y += -4.11852516267426f;
+  Y *= F;
+  Y += 6.02197014179219f;
+  Y *= F;
+  Y += -3.13396450166353f;
+  Y += E;
+  return (Y);
+}
+
+Compressor::Compressor() {}
+
+void Compressor::sumChannels(std::unique_ptr<StreamInfo> &data) {
+  tmp.resize(data->numSamples);
+  for (int i = 0; i < data->numSamples; i++) {
+    float sum = 0.0f;
+    for (auto &channel : channels) {
+      sum += data->data[channel][i];
+    }
+    tmp[i] = sum;
+  }
+}
+
+void Compressor::calLoudness() {
+  for (auto &value : tmp) {
+    value = 20 * log10f_fast(std::abs(value) + 1.0e-9f);
+    if (value >= lastLoudness) {
+      value = attack * lastLoudness + (1.0 - attack) * value;
+    } else {
+      value = release * lastLoudness + (1.0 - release) * value;
+    }
+
+    lastLoudness = value;
+  }
+}
+
+void Compressor::calGain() {
+  for (auto &value : tmp) {
+    if (value > threshold) {
+      value = -(value - threshold) * (factor - 1.0) / factor;
+    } else {
+      value = 0.0f;
+    }
+
+    value += makeupGain;
+
+    // convert to linear
+    value = pow10f(value / 20.0f);
+  }
+}
+
+void Compressor::applyGain(std::unique_ptr<StreamInfo> &data) {
+  for (int i = 0; i < data->numSamples; i++) {
+    for (auto &channel : channels) {
+      data->data[channel][i] *= tmp[i];
+    }
+  }
+}
+
+void Compressor::configure(std::vector<int> channels, float attack,
+                           float release, float threshold, float factor,
+                           float makeupGain) {
+  this->channels = channels;
+  this->attack = expf(-1000.0 / this->sampleRate / attack);
+  this->release = expf(-1000.0 / this->sampleRate / release);
+  this->threshold = threshold;
+  this->factor = factor;
+  this->makeupGain = makeupGain;
+}
+
+std::unique_ptr<StreamInfo> Compressor::process(
+    std::unique_ptr<StreamInfo> data) {
+  std::scoped_lock lock(this->accessMutex);
+  sumChannels(data);
+  calLoudness();
+  calGain();
+  applyGain(data);
+  return data;
+}