From a9980f163f03f8e306a4bdd957bd969652c9d493 Mon Sep 17 00:00:00 2001
From: Paul Ferrand <paul@ferrand.cc>
Date: Thu, 7 May 2020 01:27:20 +0200
Subject: [PATCH] Changed the historical buffer to a smoothed envelope tracker

---
 src/sfizz/Config.h  |  1 +
 src/sfizz/Voice.cpp | 44 +++++++++++++++++++++++++++++++++++++-------
 src/sfizz/Voice.h   |  5 ++++-
 3 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/src/sfizz/Config.h b/src/sfizz/Config.h
index 8a1443ac..fadba005 100644
--- a/src/sfizz/Config.h
+++ b/src/sfizz/Config.h
@@ -54,6 +54,7 @@ namespace config {
     constexpr Oversampling defaultOversamplingFactor { Oversampling::x1 };
     constexpr float A440 { 440.0 };
     constexpr size_t powerHistoryLength { 16 };
+    constexpr float filteredEnvelopeCutoff { 5 };
     constexpr uint16_t numCCs { 512 };
     constexpr int maxCurves { 256 };
     constexpr int chunkSize { 1024 };
diff --git a/src/sfizz/Voice.cpp b/src/sfizz/Voice.cpp
index 131c3670..992d97e7 100644
--- a/src/sfizz/Voice.cpp
+++ b/src/sfizz/Voice.cpp
@@ -21,6 +21,9 @@ sfz::Voice::Voice(sfz::Resources& resources)
 
     for (WavetableOscillator& osc : waveOscillators)
         osc.init(sampleRate);
+
+    for (auto & filter : channelPowerFilters)
+        filter.setGain(vaGain(config::filteredEnvelopeCutoff, sampleRate));
 }
 
 void sfz::Voice::startVoice(Region* region, int delay, int number, float value, sfz::Voice::TriggerType triggerType) noexcept
@@ -192,6 +195,9 @@ void sfz::Voice::setSampleRate(float sampleRate) noexcept
 {
     this->sampleRate = sampleRate;
 
+    for (auto & filter : channelPowerFilters)
+        filter.setGain(vaGain(config::filteredEnvelopeCutoff, sampleRate));
+
     for (WavetableOscillator& osc : waveOscillators)
         osc.init(sampleRate);
 }
@@ -207,11 +213,6 @@ void sfz::Voice::renderBlock(AudioSpan<float> buffer) noexcept
     ASSERT(static_cast<int>(buffer.getNumFrames()) <= samplesPerBlock);
     buffer.fill(0.0f);
 
-    if (state == State::idle || region == nullptr) {
-        powerHistory.push(0.0f);
-        return;
-    }
-
     const auto delay = min(static_cast<size_t>(initialDelay), buffer.getNumFrames());
     auto delayed_buffer = buffer.subspan(delay);
     initialDelay -= static_cast<int>(delay);
@@ -237,7 +238,8 @@ void sfz::Voice::renderBlock(AudioSpan<float> buffer) noexcept
     if (!egEnvelope.isSmoothing())
         reset();
 
-    powerHistory.push(buffer.meanSquared());
+    updateChannelPowers(buffer);
+
     this->triggerDelay = absl::nullopt;
 #if 0
     ASSERT(!hasNanInf(buffer.getConstSpan(0)));
@@ -629,13 +631,20 @@ void sfz::Voice::reset() noexcept
     sourcePosition = 0;
     floatPositionOffset = 0.0f;
     noteIsOff = false;
+
+    for (auto& f : channelPowerFilters)
+        f.reset();
+
+    for (auto& p : channelPowers)
+        p = 0.0f;
+
     filters.clear();
     equalizers.clear();
 }
 
 float sfz::Voice::getMeanSquaredAverage() const noexcept
 {
-    return powerHistory.getAverage();
+    return max(channelPowers[0], channelPowers[1]);
 }
 
 bool sfz::Voice::releasedOrFree() const noexcept
@@ -718,3 +727,24 @@ void sfz::Voice::setupOscillatorUnison()
     }
 #endif
 }
+
+
+void sfz::Voice::updateChannelPowers(AudioSpan<float> buffer)
+{
+    assert(channelPowers.size() == channelPowerFilters.size());
+    assert(buffer.getNumFrames() <= channelPowerFilters.size());
+    if (buffer.getNumFrames() == 0)
+        return;
+
+    auto tempSpan = resources.bufferPool.getBuffer(buffer.getNumFrames());
+    if (!tempSpan)
+        return;
+
+    for (unsigned i = 0; i < channelPowers.size(); ++i) {
+        for (unsigned s = 0; s < buffer.getNumFrames(); ++s)
+            (*tempSpan)[s] = std::abs(buffer.getConstSpan(i)[s]);
+
+        channelPowerFilters[i].processLowpass(*tempSpan, *tempSpan);
+        channelPowers[i] = tempSpan->back();
+    }
+}
diff --git a/src/sfizz/Voice.h b/src/sfizz/Voice.h
index 462cdfd7..a8d30cbf 100644
--- a/src/sfizz/Voice.h
+++ b/src/sfizz/Voice.h
@@ -13,6 +13,7 @@
 #include "Resources.h"
 #include "AudioSpan.h"
 #include "LeakDetector.h"
+#include "OnePoleFilter.h"
 #include "absl/types/span.h"
 #include <memory>
 #include <random>
@@ -245,6 +246,7 @@ private:
      * @brief Initialize frequency and gain coefficients for the oscillators.
      */
     void setupOscillatorUnison();
+    void updateChannelPowers(AudioSpan<float> buffer);
 
     Region* region { nullptr };
 
@@ -299,7 +301,8 @@ private:
 
     std::normal_distribution<float> noiseDist { 0, config::noiseVariance };
 
-    HistoricalBuffer<float> powerHistory { config::powerHistoryLength };
+    std::array<OnePoleFilter<float>, 2> channelPowerFilters;
+    std::array<float, 2> channelPowers;
     LEAK_DETECTOR(Voice);
 };