Allow modulations to trigger at a frame-accurate instant (LFO)

src/sfizz/LFO.cpp

@@ -49,7 +49,7 @@ void LFO::configure(const LFODescription* desc)
     impl_->desc_ = desc ? desc : &LFODescription::getDefault();
 }
 
-void LFO::start()
+void LFO::start(unsigned triggerDelay)
 {
     Impl& impl = *impl_;
     const LFODescription& desc = *impl.desc_;
@@ -59,7 +59,8 @@ void LFO::start()
     impl.sampleHoldMem_.fill(0.0f);
 
     const float delay = desc.delay;
-    impl.delayFramesLeft_ = (delay > 0) ? static_cast<size_t>(std::ceil(sampleRate * delay)) : 0u;
+    size_t delayFrames = (delay > 0) ? static_cast<size_t>(std::ceil(sampleRate * delay)) : 0u;
+    impl.delayFramesLeft_ = triggerDelay + delayFrames;
 
     impl.fadePosition_ = (desc.fade > 0) ? 0.0f : 1.0f;
 }

src/sfizz/LFO.h

@@ -67,7 +67,7 @@ public:
        Start processing a LFO as a region is triggered.
        Prepares the delay, phases, fade-in, etc..
      */
-    void start();
+    void start(unsigned triggerDelay);
 
     /**
        Process a cycle of the oscillator.

src/sfizz/Voice.cpp

@@ -150,7 +150,7 @@ void sfz::Voice::startVoice(Region* region, int delay, int number, float value,
     bendSmoother.reset(centsFactor(region->getBendInCents(resources.midiState.getPitchBend())));
     egEnvelope.reset(region->amplitudeEG, *region, resources.midiState, delay, value, sampleRate);
 
-    resources.modMatrix.initVoice(id, region->getId());
+    resources.modMatrix.initVoice(id, region->getId(), delay);
 }
 
 int sfz::Voice::getCurrentSampleQuality() const noexcept

src/sfizz/modulations/ModGenerator.h

@@ -36,8 +36,9 @@ public:
      *
      * @param sourceKey identifier of the source to initialize
      * @param voiceId the particular voice to initialize, if per-voice
+     * @param delay the frame time when it happens
      */
-    virtual void init(const ModKey& sourceKey, NumericId<Voice> voiceId) = 0;
+    virtual void init(const ModKey& sourceKey, NumericId<Voice> voiceId, unsigned delay) = 0;
 
     /**
      * @brief Generate a cycle of the modulator

src/sfizz/modulations/ModMatrix.cpp

@@ -196,18 +196,18 @@ void ModMatrix::init()
     for (Impl::Source &source : impl.sources_) {
         const int flags = source.key.flags();
         if (flags & kModIsPerCycle)
-            source.gen->init(source.key, {});
+            source.gen->init(source.key, {}, 0);
     }
 }
 
-void ModMatrix::initVoice(NumericId<Voice> voiceId, NumericId<Region> regionId)
+void ModMatrix::initVoice(NumericId<Voice> voiceId, NumericId<Region> regionId, unsigned delay)
 {
     Impl& impl = *impl_;
 
     for (Impl::Source &source : impl.sources_) {
         const int flags = source.key.flags();
         if ((flags & kModIsPerVoice) && source.key.region() == regionId)
-            source.gen->init(source.key, voiceId);
+            source.gen->init(source.key, voiceId, delay);
     }
 }
 

src/sfizz/modulations/ModMatrix.h

@@ -106,7 +106,7 @@ public:
      * @brief Reinitialize modulation source for a given voice.
      * This must be called first after a voice enters active state.
      */
-    void initVoice(NumericId<Voice> voiceId, NumericId<Region> regionId);
+    void initVoice(NumericId<Voice> voiceId, NumericId<Region> regionId, unsigned delay);
 
     /**
      * @brief Start modulation processing for the entire cycle.

src/sfizz/modulations/sources/Controller.cpp

@@ -49,9 +49,10 @@ void ControllerSource::setSamplesPerBlock(unsigned count)
     (void)count;
 }
 
-void ControllerSource::init(const ModKey& sourceKey, NumericId<Voice> voiceId)
+void ControllerSource::init(const ModKey& sourceKey, NumericId<Voice> voiceId, unsigned delay)
 {
     (void)voiceId;
+    (void)delay;
 
     const ModKey::Parameters p = sourceKey.parameters();
     if (p.smooth > 0) {

src/sfizz/modulations/sources/Controller.h

@@ -18,7 +18,7 @@ public:
     ~ControllerSource();
     void setSampleRate(double sampleRate) override;
     void setSamplesPerBlock(unsigned count) override;
-    void init(const ModKey& sourceKey, NumericId<Voice> voiceId) override;
+    void init(const ModKey& sourceKey, NumericId<Voice> voiceId, unsigned delay) override;
     void generate(const ModKey& sourceKey, NumericId<Voice> voiceId, absl::Span<float> buffer) override;
 
 private:

src/sfizz/modulations/sources/LFO.cpp

@@ -19,7 +19,7 @@ LFOSource::LFOSource(Synth &synth)
 {
 }
 
-void LFOSource::init(const ModKey& sourceKey, NumericId<Voice> voiceId)
+void LFOSource::init(const ModKey& sourceKey, NumericId<Voice> voiceId, unsigned delay)
 {
     Synth& synth = *synth_;
     unsigned lfoIndex = sourceKey.parameters().N;
@@ -38,7 +38,7 @@ void LFOSource::init(const ModKey& sourceKey, NumericId<Voice> voiceId)
 
     LFO* lfo = voice->getLFO(lfoIndex);
     lfo->configure(&region->lfos[lfoIndex]);
-    lfo->start();
+    lfo->start(delay);
 }
 
 void LFOSource::generate(const ModKey& sourceKey, NumericId<Voice> voiceId, absl::Span<float> buffer)

src/sfizz/modulations/sources/LFO.h

@@ -13,7 +13,7 @@ class Synth;
 class LFOSource : public ModGenerator {
 public:
     explicit LFOSource(Synth &synth);
-    void init(const ModKey& sourceKey, NumericId<Voice> voiceId) override;
+    void init(const ModKey& sourceKey, NumericId<Voice> voiceId, unsigned delay) override;
     void generate(const ModKey& sourceKey, NumericId<Voice> voiceId, absl::Span<float> buffer) override;
 
 private:

tests/LFOT.cpp

@@ -31,7 +31,7 @@ static bool computeLFO(DataPoints& dp, const fs::path& sfzPath, double sampleRat
     std::vector<float> outputMemory(numLfos * numFrames);
 
     for (size_t l = 0; l < numLfos; ++l) {
-        lfos[l].start();
+        lfos[l].start(0);
     }
 
     std::vector<absl::Span<float>> lfoOutputs(numLfos);

tests/PlotLFO.cpp

@@ -119,7 +119,7 @@ int main(int argc, char* argv[])
     std::vector<float> outputMemory(numLfos * numFrames);
 
     for (size_t l = 0; l < numLfos; ++l) {
-        lfos[l].start();
+        lfos[l].start(0);
     }
 
     std::vector<absl::Span<float>> lfoOutputs(numLfos);