Voice stealing tweaks

src/sfizz/Synth.cpp

@@ -680,6 +680,9 @@ void sfz::Synth::setSampleRate(float sampleRate) noexcept
 void sfz::Synth::renderVoiceToOutputs(Voice& voice, AudioSpan<float>& tempSpan) noexcept
 {
     const Region* region = voice.getRegion();
+    if (region == nullptr)
+        return;
+
     voice.renderBlock(tempSpan);
     for (size_t i = 0, n = effectBuses.size(); i < n; ++i) {
         if (auto& bus = effectBuses[i]) {
@@ -936,8 +939,12 @@ void sfz::Synth::noteOnDispatch(int delay, int noteNumber, float velocity) noexc
             }
 
             render:
+            // For some reason we did not find a voice to use.
+            // This is a degraded case but we'll just drop the note on.
+            if (selectedVoice == nullptr)
+                continue;
+
             // Kill voice if necessary, pre-rendering it into the output buffers
-            ASSERT(selectedVoice);
             if (!selectedVoice->isFree()) {
                 auto tempSpan = resources.bufferPool.getStereoBuffer(samplesPerBlock);
                 SisterVoiceRing::applyToRing(selectedVoice, [&] (Voice* v) {
@@ -1295,22 +1302,22 @@ void sfz::Synth::resetVoices(int numVoices)
     voices.clear();
     voices.reserve(numVoices);
 
-    for (int i = 0; i < numVoices; ++i) {
-        auto voice = absl::make_unique<Voice>(i, resources);
-        voice->setStateListener(this);
-        voices.emplace_back(std::move(voice));
-    }
-
     voiceViewArray.clear();
     voiceViewArray.reserve(numVoices);
 
     regionPolyphonyArray.clear();
     regionPolyphonyArray.reserve(numVoices);
 
+    for (int i = 0; i < numVoices; ++i) {
+        auto voice = absl::make_unique<Voice>(i, resources);
+        voice->setStateListener(this);
+        voiceViewArray.push_back(voice.get());
+        voices.emplace_back(std::move(voice));
+    }
+
     for (auto& voice : voices) {
         voice->setSampleRate(this->sampleRate);
         voice->setSamplesPerBlock(this->samplesPerBlock);
-        voiceViewArray.push_back(voice.get());
     }
 
     this->numVoices = numVoices;

src/sfizz/Voice.cpp

@@ -270,7 +270,8 @@ void sfz::Voice::renderBlock(AudioSpan<float> buffer) noexcept
     ASSERT(static_cast<int>(buffer.getNumFrames()) <= samplesPerBlock);
     buffer.fill(0.0f);
 
-    ASSERT(region != nullptr);
+    if (region == nullptr)
+        return;
 
     const auto delay = min(static_cast<size_t>(initialDelay), buffer.getNumFrames());
     auto delayed_buffer = buffer.subspan(delay);

src/sfizz/Voice.h

@@ -494,28 +494,31 @@ private:
 
 inline bool sisterVoices(const Voice* lhs, const Voice* rhs)
 {
-    return lhs->getAge() == rhs->getAge()
-        && lhs->getTriggerNumber() == rhs->getTriggerNumber()
-        && lhs->getTriggerValue() == rhs->getTriggerValue()
-        && lhs->getTriggerType() == rhs->getTriggerType();
+    if (lhs->getAge() != rhs->getAge())
+        return false;
+
+    if (lhs->getTriggerNumber() != rhs->getTriggerNumber())
+        return false;
+
+    if (lhs->getTriggerValue() != rhs->getTriggerValue())
+        return false;
+
+    if (lhs->getTriggerType() != rhs->getTriggerType())
+        return false;
+
+    return true;
 }
 
 inline bool voiceOrdering(const Voice* lhs, const Voice* rhs)
 {
     if (lhs->getAge() > rhs->getAge())
         return true;
-    if (lhs->getAge() < rhs->getAge())
-        return false;
 
-    if (lhs->getTriggerNumber() > rhs->getTriggerNumber())
-        return true;
     if (lhs->getTriggerNumber() < rhs->getTriggerNumber())
-        return false;
-
-    if (lhs->getTriggerValue() > rhs->getTriggerValue())
         return true;
+
     if (lhs->getTriggerValue() < rhs->getTriggerValue())
-        return false;
+        return true;
 
     if (lhs->getTriggerType() > rhs->getTriggerType())
         return true;

src/sfizz/VoiceStealing.cpp

@@ -8,7 +8,7 @@ sfz::VoiceStealing::VoiceStealing()
 sfz::Voice* sfz::VoiceStealing::steal(absl::Span<sfz::Voice*> voices) noexcept
 {
     // Start of the voice stealing algorithm
-    absl::c_sort(voices, voiceOrdering);
+    absl::c_stable_sort(voices, voiceOrdering);
 
     const auto sumEnvelope = absl::c_accumulate(voices, 0.0f, [](float sum, const Voice* v) {
         return sum + v->getAverageEnvelope();
@@ -21,9 +21,8 @@ sfz::Voice* sfz::VoiceStealing::steal(absl::Span<sfz::Voice*> voices) noexcept
     // This is not perfect because pad-type voices will take a long time to output
     // their sound, but it's reasonable for sounds with a quick attack and longer
     // release.
-    const auto ageThreshold = voices.front()->getAge() * config::stealingAgeCoeff;
-    // This needs to be positive
-    ASSERT(ageThreshold >= 0);
+    const auto ageThreshold =
+        static_cast<int>(voices.front()->getAge() * config::stealingAgeCoeff) + 1;
 
     Voice* returnedVoice = voices.front();
     unsigned idx = 0;
@@ -49,5 +48,10 @@ sfz::Voice* sfz::VoiceStealing::steal(absl::Span<sfz::Voice*> voices) noexcept
         do { idx++; }
         while (idx < voices.size() && sisterVoices(ref, voices[idx]));
     }
+
+    // Guard for future changes: voices with age 0 just started; don't kill those.
+    if (returnedVoice->getAge() == 0)
+        return {};
+
     return returnedVoice;
 }