Smooth the crossfades

src/sfizz/Config.h

@@ -41,6 +41,7 @@ namespace config {
     constexpr int numVoices { 64 };
     constexpr unsigned maxVoices { 256 };
     constexpr unsigned smoothingSteps { 512 };
+    constexpr uint8_t xfadeSmoothing { 5 };
     constexpr uint8_t gainSmoothing { 0 };
     constexpr unsigned powerTableSizeExponent { 11 };
     constexpr int maxFilePromises { maxVoices };

src/sfizz/Voice.cpp

@@ -25,6 +25,7 @@ sfz::Voice::Voice(int voiceNumber, sfz::Resources& resources)
         osc.init(sampleRate);
 
     gainSmoother.setSmoothing(config::gainSmoothing, sampleRate);
+    xfadeSmoother.setSmoothing(config::xfadeSmoothing, sampleRate);
 
     for (auto & filter : channelEnvelopeFilters)
         filter.setGain(vaGain(config::filteredEnvelopeCutoff, sampleRate));
@@ -245,6 +246,7 @@ void sfz::Voice::setSampleRate(float sampleRate) noexcept
 {
     this->sampleRate = sampleRate;
     gainSmoother.setSmoothing(config::gainSmoothing, sampleRate);
+    xfadeSmoother.setSmoothing(config::xfadeSmoothing, sampleRate);
 
     for (auto & filter : channelEnvelopeFilters)
         filter.setGain(vaGain(config::filteredEnvelopeCutoff, sampleRate));
@@ -308,11 +310,45 @@ void sfz::Voice::renderBlock(AudioSpan<float> buffer) noexcept
 #endif
 }
 
-void sfz::Voice::amplitudeEnvelope(absl::Span<float> modulationSpan) noexcept
+void sfz::Voice::applyCrossfades(absl::Span<float> modulationSpan) noexcept
 {
     const auto numSamples = modulationSpan.size();
     const auto xfCurve = region->crossfadeCCCurve;
 
+    auto tempSpan = resources.bufferPool.getBuffer(numSamples);
+    if (!tempSpan)
+        return;
+
+    bool smoothOutput = false;
+    for (const auto& mod : region->crossfadeCCInRange) {
+        const auto events = resources.midiState.getCCEvents(mod.cc);
+        smoothOutput |= (events.size() > 1);
+        linearEnvelope(events, *tempSpan, [&](float x) {
+            return crossfadeIn(mod.data, x, xfCurve);
+        });
+        applyGain<float>(*tempSpan, modulationSpan);
+    }
+
+    for (const auto& mod : region->crossfadeCCOutRange) {
+        const auto events = resources.midiState.getCCEvents(mod.cc);
+        smoothOutput |= (events.size() > 1);
+        linearEnvelope(events, *tempSpan, [&](float x) {
+            return crossfadeOut(mod.data, x, xfCurve);
+        });
+        applyGain<float>(*tempSpan, modulationSpan);
+    }
+
+    if (smoothOutput) {
+        xfadeSmoother.reset(modulationSpan.front());
+        xfadeSmoother.process(modulationSpan, modulationSpan);
+    }
+}
+
+
+void sfz::Voice::amplitudeEnvelope(absl::Span<float> modulationSpan) noexcept
+{
+    const auto numSamples = modulationSpan.size();
+
     auto tempSpan = resources.bufferPool.getBuffer(numSamples);
     if (!tempSpan)
         return;
@@ -328,22 +364,6 @@ void sfz::Voice::amplitudeEnvelope(absl::Span<float> modulationSpan) noexcept
         applyGain<float>(*tempSpan, modulationSpan);
     });
 
-    // Crossfade envelopes
-    for (const auto& mod : region->crossfadeCCInRange) {
-        const auto events = resources.midiState.getCCEvents(mod.cc);
-        linearEnvelope(events, *tempSpan, [&](float x) {
-            return crossfadeIn(mod.data, x, xfCurve);
-        });
-        applyGain<float>(*tempSpan, modulationSpan);
-    }
-    for (const auto& mod : region->crossfadeCCOutRange) {
-        const auto events = resources.midiState.getCCEvents(mod.cc);
-        linearEnvelope(events, *tempSpan, [&](float x) {
-            return crossfadeOut(mod.data, x, xfCurve);
-        });
-        applyGain<float>(*tempSpan, modulationSpan);
-    }
-
     // Volume envelope
     applyGain1<float>(db2mag(baseVolumedB), modulationSpan);
     forEachWithSmoother(Mod::volume, [&](const CCData<Modifier>& mod, Smoother& smoother) {
@@ -370,6 +390,7 @@ void sfz::Voice::ampStageMono(AudioSpan<float> buffer) noexcept
         return;
 
     amplitudeEnvelope(*modulationSpan);
+    applyCrossfades(*modulationSpan);
     applyGain<float>(*modulationSpan, leftBuffer);
 }
 
@@ -383,6 +404,7 @@ void sfz::Voice::ampStageStereo(AudioSpan<float> buffer) noexcept
         return;
 
     amplitudeEnvelope(*modulationSpan);
+    applyCrossfades(*modulationSpan);
     buffer.applyGain(*modulationSpan);
 }
 

src/sfizz/Voice.h

@@ -340,6 +340,14 @@ private:
      * @param modulationSpan
      */
     void amplitudeEnvelope(absl::Span<float> modulationSpan) noexcept;
+
+    /**
+     * @brief Apply the crossfade envelope to a span.
+     *
+     * @param modulationSpan
+     */
+    void applyCrossfades(absl::Span<float> modulationSpan) noexcept;
+
     /**
      * @brief Amplitude stage for a mono source
      *
@@ -473,6 +481,7 @@ private:
     ModifierArray<std::vector<Smoother>> modifierSmoothers;
     Smoother gainSmoother;
     Smoother bendSmoother;
+    Smoother xfadeSmoother;
     void resetSmoothers() noexcept;
 
     std::array<OnePoleFilter<float>, 2> channelEnvelopeFilters;