Add more voices than necessary

These will naturally be used for "dying" voices beyond the engine polyphony

src/sfizz/Config.h

@@ -131,6 +131,13 @@ namespace config {
     static constexpr int loopXfadeCurve = 2;    // 0: linear
                                                 // 1: use curves 5 & 6
                                                 // 2: use S-shaped curve
+    /**
+     * @brief Overflow voices in the engine, relative to the required voices.
+     * These are additional voices that more or less hold the "dying" voices
+     * due to engine polyphony being reached.
+     */
+    static constexpr float overflowVoiceMultiplier { 1.5f };
+    static_assert(overflowVoiceMultiplier >= 1.0f);
 } // namespace config
 
 } // namespace sfz

src/sfizz/RegionSet.cpp

@@ -53,3 +53,8 @@ unsigned sfz::RegionSet::numPlayingVoices() const noexcept
         return !v->releasedOrFree();
     });
 }
+
+void sfz::RegionSet::removeAllVoices() noexcept
+{
+    voices.clear();
+}

src/sfizz/RegionSet.h

@@ -122,6 +122,11 @@ public:
      * @return const std::vector<RegionSet*>&
      */
     const std::vector<RegionSet*>& getSubsets() const noexcept { return subsets; }
+
+    /**
+     * @brief Remove all voices from the set
+     */
+    void removeAllVoices() noexcept;
 private:
     RegionSet* parent { nullptr };
     OpcodeScope level { kOpcodeScopeGeneric };

src/sfizz/Synth.cpp

@@ -41,6 +41,7 @@ sfz::Synth::Synth(int numVoices)
     initializeSIMDDispatchers();
 
     const std::lock_guard<SpinMutex> disableCallback { callbackGuard };
+    engineSet = absl::make_unique<RegionSet>(nullptr, OpcodeScope::kOpcodeScopeGeneric);
     parser.setListener(this);
     effectFactory.registerStandardEffectTypes();
     effectBuses.reserve(5); // sufficient room for main and fx1-4
@@ -387,6 +388,7 @@ void sfz::Synth::handleControlOpcodes(const std::vector<Opcode>& members)
             default:
                 DBG("Unsupported value for hint_stealing: " << member.value);
             }
+            break;
         default:
             // Unsupported control opcode
             DBG("Unsupported control opcode: " << member.opcode);
@@ -742,23 +744,8 @@ sfz::Voice* sfz::Synth::findFreeVoice() noexcept
     if (freeVoice != voices.end())
         return freeVoice->get();
 
-    // Engine polyphony reached
-    Voice* stolenVoice = stealer.steal(absl::MakeSpan(voiceViewArray));
-    if (stolenVoice == nullptr)
-        return {};
-
-    // Never kill age 0 voices
-    if (stolenVoice->getAge() == 0)
-        return {};
-
-
-    auto tempSpan = resources.bufferPool.getStereoBuffer(samplesPerBlock);
-    SisterVoiceRing::applyToRing(stolenVoice, [&] (Voice* v) {
-        renderVoiceToOutputs(*v, *tempSpan);
-        v->reset();
-    });
-
-    return stolenVoice;
+    DBG("Engine polyphony reached");
+    return {};
 }
 
 int sfz::Synth::getNumActiveVoices(bool recompute) const noexcept
@@ -1511,7 +1498,7 @@ void sfz::Synth::setVolume(float volume) noexcept
 
 int sfz::Synth::getNumVoices() const noexcept
 {
-    return numVoices;
+    return numRequiredVoices;
 }
 
 void sfz::Synth::setNumVoices(int numVoices) noexcept
@@ -1520,7 +1507,7 @@ void sfz::Synth::setNumVoices(int numVoices) noexcept
     const std::lock_guard<SpinMutex> disableCallback { callbackGuard };
 
     // fast path
-    if (numVoices == this->numVoices)
+    if (numVoices == this->numRequiredVoices)
         return;
 
     resetVoices(numVoices);
@@ -1528,16 +1515,25 @@ void sfz::Synth::setNumVoices(int numVoices) noexcept
 
 void sfz::Synth::resetVoices(int numVoices)
 {
+    numActualVoices =
+        static_cast<int>(config::overflowVoiceMultiplier * numVoices);
+    numRequiredVoices = numVoices;
+
+    for (auto& set : sets)
+        set->removeAllVoices();
+    engineSet->removeAllVoices();
+    engineSet->setPolyphonyLimit(numRequiredVoices);
+
     voices.clear();
-    voices.reserve(numVoices);
+    voices.reserve(numActualVoices);
 
     voiceViewArray.clear();
-    voiceViewArray.reserve(numVoices);
+    voiceViewArray.reserve(numActualVoices);
 
     tempPolyphonyArray.clear();
-    tempPolyphonyArray.reserve(numVoices);
+    tempPolyphonyArray.reserve(numActualVoices);
 
-    for (int i = 0; i < numVoices; ++i) {
+    for (int i = 0; i < numActualVoices; ++i) {
         auto voice = absl::make_unique<Voice>(i, resources);
         voice->setStateListener(this);
         voiceViewArray.push_back(voice.get());
@@ -1549,8 +1545,6 @@ void sfz::Synth::resetVoices(int numVoices)
         voice->setSamplesPerBlock(this->samplesPerBlock);
     }
 
-    this->numVoices = numVoices;
-
     applySettingsPerVoice();
 }
 

src/sfizz/Synth.h

@@ -819,6 +819,9 @@ private:
     // These are more general "groups" than sfz and encapsulates the full hierarchy
     RegionSet* currentSet { nullptr };
     std::vector<RegionSetPtr> sets;
+    // This region set holds the engine set of voices, which tries to respect the required
+    // engine polyphony
+    RegionSetPtr engineSet;
 
     // These are the `group=` groups where you can off voices
     std::vector<PolyphonyGroup> polyphonyGroups;
@@ -902,7 +905,8 @@ private:
     int samplesPerBlock { config::defaultSamplesPerBlock };
     float sampleRate { config::defaultSampleRate };
     float volume { Default::globalVolume };
-    int numVoices { config::numVoices };
+    int numRequiredVoices { config::numVoices };
+    int numActualVoices { static_cast<int>(config::numVoices * config::overflowVoiceMultiplier) };
     int activeVoices { 0 };
     Oversampling oversamplingFactor { config::defaultOversamplingFactor };