Move the power follower to its own file

dpf.mk

@@ -103,6 +103,7 @@ SFIZZ_SOURCES = \
 	src/sfizz/Parser.cpp \
 	src/sfizz/parser/Parser.cpp \
 	src/sfizz/parser/ParserPrivate.cpp \
+	src/sfizz/PowerFollower.cpp \
 	src/sfizz/Region.cpp \
 	src/sfizz/RTSemaphore.cpp \
 	src/sfizz/ScopedFTZ.cpp \

src/CMakeLists.txt

@@ -81,6 +81,7 @@ set (SFIZZ_HEADERS
     sfizz/Oversampler.h
     sfizz/Panning.h
     sfizz/PolyphonyGroup.h
+    sfizz/PowerFollower.h
     sfizz/railsback/2-1.h
     sfizz/railsback/4-1.h
     sfizz/railsback/4-2.h
@@ -138,6 +139,7 @@ set (SFIZZ_SOURCES
     sfizz/Effects.cpp
     sfizz/LFO.cpp
     sfizz/LFODescription.cpp
+    sfizz/PowerFollower.cpp
     sfizz/modulations/ModId.cpp
     sfizz/modulations/ModKey.cpp
     sfizz/modulations/ModKeyHash.cpp

src/sfizz/PowerFollower.cpp

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: BSD-2-Clause
+
+// This code is part of the sfizz library and is licensed under a BSD 2-clause
+// license. You should have receive a LICENSE.md file along with the code.
+// If not, contact the sfizz maintainers at https://github.com/sfztools/sfizz
+
+#include "PowerFollower.h"
+#include "Defaults.h"
+#include "SIMDHelpers.h"
+#include <absl/types/span.h>
+
+namespace sfz {
+
+PowerFollower::PowerFollower()
+    : sampleRate_(config::defaultSampleRate),
+      samplesPerBlock_(config::defaultSamplesPerBlock),
+      tempBuffer_(new float[config::defaultSamplesPerBlock])
+{
+    updateTrackingFactor();
+}
+
+void PowerFollower::setSampleRate(float sampleRate) noexcept
+{
+    if (sampleRate_ != sampleRate) {
+        sampleRate_ = sampleRate;
+        updateTrackingFactor();
+    }
+}
+
+void PowerFollower::setSamplesPerBlock(unsigned samplesPerBlock)
+{
+    if (samplesPerBlock_ != samplesPerBlock) {
+        tempBuffer_.reset(new float[samplesPerBlock]);
+        samplesPerBlock_ = samplesPerBlock;
+        updateTrackingFactor();
+    }
+}
+
+void PowerFollower::process(AudioSpan<float> buffer) noexcept
+{
+    size_t numFrames = buffer.getNumFrames();
+    if (numFrames == 0)
+        return;
+
+    absl::Span<float> tempBuffer(tempBuffer_.get(), numFrames);
+
+    copy(buffer.getConstSpan(0), tempBuffer);
+    for (unsigned i = 1; i < buffer.getNumChannels(); ++i)
+        add(buffer.getConstSpan(i), tempBuffer);
+
+    const float meanPower = meanSquared<float>(tempBuffer);
+
+    const float attackFactor = static_cast<float>(buffer.getNumFrames()) * attackTrackingFactor_;
+    const float releaseFactor = static_cast<float>(buffer.getNumFrames()) * releaseTrackingFactor_;
+
+    meanChannelPower_ = max(
+        meanChannelPower_ * (1 - attackFactor) + meanPower * attackFactor,
+        meanChannelPower_ * (1 - releaseFactor) + meanPower * releaseFactor
+    );
+}
+
+void PowerFollower::clear() noexcept
+{
+    meanChannelPower_ = 0;
+}
+
+void PowerFollower::updateTrackingFactor() noexcept
+{
+    // Protect the envelope follower against blowups
+    const auto maxTrackingFactor = sampleRate_ / samplesPerBlock_;
+    attackTrackingFactor_ =  min(config::powerFollowerAttackFactor, maxTrackingFactor) / sampleRate_;
+    releaseTrackingFactor_ =  min(config::powerFollowerReleaseFactor, maxTrackingFactor) / sampleRate_;
+}
+
+} // namespace sfz

src/sfizz/PowerFollower.h

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: BSD-2-Clause
+
+// This code is part of the sfizz library and is licensed under a BSD 2-clause
+// license. You should have receive a LICENSE.md file along with the code.
+// If not, contact the sfizz maintainers at https://github.com/sfztools/sfizz
+
+#pragma once
+#include "AudioSpan.h"
+#include <memory>
+
+namespace sfz {
+
+class PowerFollower {
+public:
+    PowerFollower();
+    void setSampleRate(float sampleRate) noexcept;
+    void setSamplesPerBlock(unsigned samplesPerBlock);
+    void process(AudioSpan<float> buffer) noexcept;
+    void clear() noexcept;
+    float getAveragePower() const noexcept { return meanChannelPower_; }
+
+private:
+    void updateTrackingFactor() noexcept;
+
+private:
+    float sampleRate_ {};
+    unsigned samplesPerBlock_ {};
+
+    std::unique_ptr<float[]> tempBuffer_;
+
+    float attackTrackingFactor_ {};
+    float releaseTrackingFactor_ {};
+
+    float meanChannelPower_ {};
+};
+
+} // namespace sfz

src/sfizz/Voice.cpp

@@ -237,14 +237,6 @@ void sfz::Voice::registerTempo(int delay, float secondsPerQuarter) noexcept
     UNUSED(secondsPerQuarter);
 }
 
-void sfz::Voice::updateTrackingFactor() noexcept
-{
-    // Protect the envelope follower against blowups
-    const auto maxTrackingFactor = sampleRate / samplesPerBlock;
-    attackTrackingFactor =  min(config::powerFollowerAttackFactor, maxTrackingFactor) / sampleRate;
-    releaseTrackingFactor =  min(config::powerFollowerReleaseFactor, maxTrackingFactor) / sampleRate;
-}
-
 void sfz::Voice::setSampleRate(float sampleRate) noexcept
 {
     this->sampleRate = sampleRate;
@@ -257,13 +249,13 @@ void sfz::Voice::setSampleRate(float sampleRate) noexcept
     for (auto& lfo : lfos)
         lfo->setSampleRate(sampleRate);
 
-    updateTrackingFactor();
+    powerFollower.setSampleRate(sampleRate);
 }
 
 void sfz::Voice::setSamplesPerBlock(int samplesPerBlock) noexcept
 {
     this->samplesPerBlock = samplesPerBlock;
-    updateTrackingFactor();
+    powerFollower.setSamplesPerBlock(samplesPerBlock);
 }
 
 void sfz::Voice::renderBlock(AudioSpan<float> buffer) noexcept
@@ -299,7 +291,7 @@ void sfz::Voice::renderBlock(AudioSpan<float> buffer) noexcept
     if (!egEnvelope.isSmoothing())
         switchState(State::cleanMeUp);
 
-    updateChannelPowers(buffer);
+    powerFollower.process(buffer);
 
     age += buffer.getNumFrames();
     if (triggerDelay) {
@@ -740,7 +732,7 @@ void sfz::Voice::reset() noexcept
     floatPositionOffset = 0.0f;
     noteIsOff = false;
 
-    meanChannelPower = 0.0f;
+    powerFollower.clear();
 
     filters.clear();
     equalizers.clear();
@@ -772,7 +764,7 @@ void sfz::Voice::removeVoiceFromRing() noexcept
 
 float sfz::Voice::getAveragePower() const noexcept
 {
-    return meanChannelPower;
+    return powerFollower.getAveragePower();
 }
 
 bool sfz::Voice::releasedOrFree() const noexcept
@@ -867,31 +859,6 @@ void sfz::Voice::setupOscillatorUnison()
 #endif
 }
 
-void sfz::Voice::updateChannelPowers(AudioSpan<float> buffer)
-{
-    if (buffer.getNumFrames() == 0)
-        return;
-
-    auto tempBuffer = resources.bufferPool.getBuffer(buffer.getNumFrames());
-    if (!tempBuffer)
-        return;
-
-    sfz::copy(buffer.getConstSpan(0), *tempBuffer);
-    for (unsigned i = 1; i < buffer.getNumChannels(); ++i)
-        sfz::add(buffer.getConstSpan(i), *tempBuffer);
-
-    const float meanPower = sfz::meanSquared<float>(*tempBuffer);
-
-    const float attackFactor = static_cast<float>(buffer.getNumFrames()) * attackTrackingFactor;
-    const float releaseFactor = static_cast<float>(buffer.getNumFrames()) * releaseTrackingFactor;
-
-    meanChannelPower = max(
-        meanChannelPower * (1 - attackFactor) + meanPower * attackFactor,
-        meanChannelPower * (1 - releaseFactor) + meanPower * releaseFactor
-    );
-}
-
-
 void sfz::Voice::switchState(State s)
 {
     if (s != state) {

src/sfizz/Voice.h

@@ -15,6 +15,7 @@
 #include "AudioSpan.h"
 #include "LeakDetector.h"
 #include "OnePoleFilter.h"
+#include "PowerFollower.h"
 #include "NumericId.h"
 #include "absl/types/span.h"
 #include <memory>
@@ -485,15 +486,8 @@ private:
     Smoother xfadeSmoother;
     void resetSmoothers() noexcept;
 
-    /**
-     * @brief Update and clamp the tracking factors to ensure the power
-     *          follower does not blow up.
-     *
-     */
-    void updateTrackingFactor() noexcept;
-    float attackTrackingFactor { config::powerFollowerAttackFactor / config::defaultSampleRate };
-    float releaseTrackingFactor { config::powerFollowerReleaseFactor / config::defaultSampleRate };
-    float meanChannelPower;
+    PowerFollower powerFollower;
+
     LEAK_DETECTOR(Voice);
 };