From 42d259462a4cadab0db3751c08a741e7e762523a Mon Sep 17 00:00:00 2001
From: Jean Pierre Cimalando <jp-dev@inbox.ru>
Date: Thu, 6 May 2021 22:21:03 +0200
Subject: [PATCH] Eliminate unneeded computation

---
 sources/dsp/MultirateSTFT.cpp    |  5 +++++
 sources/dsp/STFT.cpp             |  8 +++++---
 sources/dsp/SpectralAnalyzer.cpp | 19 ++++++++++++++++++-
 sources/dsp/SpectralAnalyzer.h   |  7 +++++++
 4 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/sources/dsp/MultirateSTFT.cpp b/sources/dsp/MultirateSTFT.cpp
index 3a47d2d..06fce31 100644
--- a/sources/dsp/MultirateSTFT.cpp
+++ b/sources/dsp/MultirateSTFT.cpp
@@ -20,6 +20,11 @@ void MultirateSTFT<Rates>::configure(const Configuration &config)
         rateConfig[r].stepSize = config.stepSize / (1u << r);
         rateConfig[r].sampleRate = config.sampleRate / (1u << r);
         fStft[r].configure(rateConfig[r]);
+
+        if (r == Rates - 1)
+            fStft[r].configureBinRange(0, specSize);
+        else
+            fStft[r].configureBinRange(specSize / 2, specSize);
     }
 
     //
diff --git a/sources/dsp/STFT.cpp b/sources/dsp/STFT.cpp
index 0aa8ea9..eb4515f 100644
--- a/sources/dsp/STFT.cpp
+++ b/sources/dsp/STFT.cpp
@@ -2,8 +2,6 @@
 #include "FFTPlanner.h"
 #include "AnalyzerDefs.h"
 #include <algorithm>
-#include <unordered_map>
-#include <mutex>
 #include <cmath>
 
 void STFT::configure(const Configuration &config)
@@ -31,8 +29,12 @@ void STFT::processNewBlock(float *input)
     std::complex<float> *cpx = _cpx.data();
     fftwf_execute_dft_r2c(plan, input, (fftwf_complex *)cpx);
 
+    const uint32_t *binRange = getBinRange();
+    uint32_t start = binRange[0];
+    uint32_t end = std::min(binRange[1], numBins);
+
     float *mag = getMagnitudes();
-    for (uint32_t i = 0; i < numBins; ++i) {
+    for (uint32_t i = start; i < end; ++i) {
         double linear = std::abs(cpx[i]) * (2.0f / windowSize);
         double decibel = 20.0 * std::log10(std::max(kStftFloorMagnitude, linear));
         mag[i] = decibel;
diff --git a/sources/dsp/SpectralAnalyzer.cpp b/sources/dsp/SpectralAnalyzer.cpp
index baa0527..6adfe2f 100644
--- a/sources/dsp/SpectralAnalyzer.cpp
+++ b/sources/dsp/SpectralAnalyzer.cpp
@@ -36,6 +36,13 @@ void SteppingAnalyzer::configureStepping(uint32_t numBins, const Configuration &
     _smoother.configure(numBins, config.stepSize, config.attackTime, config.releaseTime, config.sampleRate);
 }
 
+void SteppingAnalyzer::configureBinRange(uint32_t start, uint32_t end)
+{
+    _binRange[0] = start;
+    _binRange[1] = end;
+    _smoother.configureBinRange(start, end);
+}
+
 void SteppingAnalyzer::setAttackAndRelease(float attack, float release)
 {
     _smoother.setAttackAndRelease(attack, release);
@@ -92,6 +99,12 @@ void SteppingAnalyzer::Smoother::configure(uint32_t numBins, uint32_t stepSize,
     setAttackAndRelease(attackTime, releaseTime);
 }
 
+void SteppingAnalyzer::Smoother::configureBinRange(uint32_t start, uint32_t end)
+{
+    _binRange[0] = start;
+    _binRange[1] = end;
+}
+
 void SteppingAnalyzer::Smoother::setAttackAndRelease(float attack, float release)
 {
     ARFollower *ar = _ar.data();
@@ -115,6 +128,10 @@ void SteppingAnalyzer::Smoother::process(float *stepData)
 {
     ARFollower *ar = _ar.data();
     uint32_t numBins = (uint32_t)_ar.size();
-    for (uint32_t i = 0; i < numBins; ++i)
+
+    uint32_t start = _binRange[0];
+    uint32_t end = std::min(_binRange[1], numBins);
+
+    for (uint32_t i = start; i < end; ++i)
         stepData[i] = ar[i].compute(stepData[i]);
 }
diff --git a/sources/dsp/SpectralAnalyzer.h b/sources/dsp/SpectralAnalyzer.h
index ab247de..b33ad8e 100644
--- a/sources/dsp/SpectralAnalyzer.h
+++ b/sources/dsp/SpectralAnalyzer.h
@@ -47,11 +47,13 @@ class SteppingAnalyzer : public BasicAnalyzer {
 
 public:
     uint32_t getWindowSize() const { return _windowSize; }
+    const uint32_t *getBinRange() const { return _binRange; }
 
 protected:
     void configureStepping(uint32_t numBins, const Configuration &config);
 
 public:
+    virtual void configureBinRange(uint32_t start, uint32_t end);
     virtual void setAttackAndRelease(float attack, float release) override;
     virtual void clear() override;
     virtual void process(const float *input, uint32_t numFrames) override;
@@ -72,6 +74,9 @@ class SteppingAnalyzer : public BasicAnalyzer {
     uint32_t _ringIndex {};
     std::vector<float> _ring;
 
+    // range
+    uint32_t _binRange[2] = { 0u, ~0u };
+
     // temporary
     std::vector<float> _input;
 
@@ -79,12 +84,14 @@ class SteppingAnalyzer : public BasicAnalyzer {
     class Smoother {
     public:
         void configure(uint32_t numBins, uint32_t stepSize, double attackTime, double releaseTime, double sampleRate);
+        void configureBinRange(uint32_t start, uint32_t end);
         void setAttackAndRelease(float attack, float release);
         void clear();
         void process(float *stepData);
     private:
         std::vector<ARFollower> _ar;
         uint32_t _stepSize = 0;
+        uint32_t _binRange[2] = { 0u, ~0u };
     };
     Smoother _smoother;
 };