Advance the generator when not used

src/sfizz/Synth.cpp

@@ -723,6 +723,7 @@ void sfz::Synth::renderBlock(AudioSpan<float> buffer) noexcept
     }
 
     ModMatrix& mm = resources.modMatrix;
+    mm.beginCycle(numFrames);
 
     activeVoices = 0;
     { // Main render block
@@ -731,8 +732,6 @@ void sfz::Synth::renderBlock(AudioSpan<float> buffer) noexcept
         tempMixSpan->fill(0.0f);
         resources.filePool.cleanupPromises();
 
-        mm.beginCycle(numFrames);
-
         // Ramp out whatever is in the buffer at this point; should only be killed voice data
         linearRamp<float>(*rampSpan, 1.0f, -1.0f / static_cast<float>(numFrames));
         for (size_t i = 0, n = effectBuses.size(); i < n; ++i) {
@@ -754,6 +753,8 @@ void sfz::Synth::renderBlock(AudioSpan<float> buffer) noexcept
             callbackBreakdown.filters += voice->getLastFilterDuration();
             callbackBreakdown.panning += voice->getLastPanningDuration();
 
+            mm.endVoice();
+
             if (voice->toBeCleanedUp())
                 voice->reset();
         }
@@ -781,6 +782,9 @@ void sfz::Synth::renderBlock(AudioSpan<float> buffer) noexcept
     // Apply the master volume
     buffer.applyGain(db2mag(volume));
 
+    // Perform any remaining modulators
+    mm.endCycle();
+
     { // Clear events and advance midi time
         ScopedTiming logger { dispatchDuration, ScopedTiming::Operation::addToDuration };
         resources.midiState.advanceTime(buffer.getNumFrames());

src/sfizz/modulations/ModGenerator.h

@@ -47,6 +47,20 @@ public:
      * @param buffer output buffer
      */
     virtual void generate(const ModKey& sourceKey, NumericId<Voice> voiceNum, absl::Span<float> buffer) = 0;
+
+    /**
+     * @brief Advance the generator by a number of frames
+     * This is called instead of `generate` in case the output is discarded.
+     * It can be overriden with a faster implementation if wanted.
+     *
+     * @param sourceKey source key
+     * @param voiceNum voice number if the generator is per-voice, otherwise undefined
+     * @param buffer writable spare buffer, contents will be discarded
+     */
+    virtual void generateDiscarded(const ModKey& sourceKey, NumericId<Voice> voiceNum, absl::Span<float> buffer)
+    {
+        generate(sourceKey, voiceNum, buffer);
+    }
 };
 
 } // namespace sfz

src/sfizz/modulations/ModMatrix.cpp

@@ -224,6 +224,22 @@ void ModMatrix::beginCycle(unsigned numFrames)
         target.bufferReady = false;
 }
 
+void ModMatrix::endCycle()
+{
+    Impl& impl = *impl_;
+    const uint32_t numFrames = impl.numFrames_;
+
+    for (Impl::Source &source : impl.sources_) {
+        if (!source.bufferReady) {
+            int flags = source.key.flags();
+            if (flags & kModIsPerCycle) {
+                absl::Span<float> buffer(source.buffer.data(), numFrames);
+                source.gen->generateDiscarded(source.key, {}, buffer);
+            }
+        }
+    }
+}
+
 void ModMatrix::beginVoice(NumericId<Voice> voiceId)
 {
     Impl& impl = *impl_;
@@ -242,6 +258,23 @@ void ModMatrix::beginVoice(NumericId<Voice> voiceId)
     }
 }
 
+void ModMatrix::endVoice()
+{
+    Impl& impl = *impl_;
+    const uint32_t numFrames = impl.numFrames_;
+    const NumericId<Voice> voiceId = impl.voiceId_;
+
+    for (Impl::Source &source : impl.sources_) {
+        if (!source.bufferReady) {
+            int flags = source.key.flags();
+            if (flags & kModIsPerVoice) {
+                absl::Span<float> buffer(source.buffer.data(), numFrames);
+                source.gen->generateDiscarded(source.key, voiceId, buffer);
+            }
+        }
+    }
+}
+
 float* ModMatrix::getModulation(TargetId targetId)
 {
     if (!validTarget(targetId))

src/sfizz/modulations/ModMatrix.h

@@ -113,6 +113,12 @@ public:
      */
     void beginCycle(unsigned numFrames);
 
+    /**
+     * @brief End modulation processing for the entire cycle.
+     * This performs a dummy run of any unused modulations.
+     */
+    void endCycle();
+
     /**
      * @brief Start modulation processing for a given voice.
      * This clears all the buffers which are per-voice.
@@ -121,6 +127,12 @@ public:
      */
     void beginVoice(NumericId<Voice> voiceId);
 
+    /**
+     * @brief End modulation processing for a given voice.
+     * This performs a dummy run of any unused modulations which are per-cycle.
+     */
+    void endVoice();
+
     /**
      * @brief Get the modulation buffer for the given target.
      * If the target does not exist, the result is null.