Add the opcode sample_quality and default value to 2

src/sfizz/AudioSpan.h

@@ -246,7 +246,7 @@ public:
      * @param channelIndex the channel
      * @return absl::Span<const Type>
      */
-    absl::Span<const Type> getConstSpan(size_t channelIndex)
+    absl::Span<const Type> getConstSpan(size_t channelIndex) const
     {
         ASSERT(channelIndex < numChannels);
         if (channelIndex < numChannels)
@@ -382,7 +382,7 @@ public:
      *
      * @returns size_type the number of frames in the AudioSpan
      */
-    size_type getNumFrames()
+    size_type getNumFrames() const
     {
         return numFrames;
     }
@@ -392,7 +392,7 @@ public:
      *
      * @returns size_type the number of channels in the AudioSpan
      */
-    size_t getNumChannels()
+    size_t getNumChannels() const
     {
         return numChannels;
     }

src/sfizz/Defaults.h

@@ -221,6 +221,9 @@ namespace Default
 	constexpr Range<float> egOnCCPercentRange { -100.0, 100.0 };
 
     // ***** SFZ v2 ********
+    constexpr int sampleQuality { 2 };
+    constexpr Range<int> sampleQualityRange { 1, 10 }; // sample_quality
+
 	constexpr bool checkSustain { true }; // sustain_sw
 	constexpr bool checkSostenuto { true }; // sostenuto_sw
     constexpr Range<int> octaveOffsetRange { -10, 10 }; // octave_offset

src/sfizz/Region.cpp

@@ -60,6 +60,12 @@ bool sfz::Region::parseOpcode(const Opcode& rawOpcode)
             sampleId = FileId(std::move(filename), sampleId.isReverse());
         }
         break;
+    case hash("sample_quality"):
+        {
+            setValueFromOpcode(opcode, sampleQuality, Default::sampleQualityRange);
+            break;
+        }
+        break;
     case hash("direction"):
         sampleId = sampleId.reversed(opcode.value == "reverse");
         break;

src/sfizz/Region.h

@@ -240,6 +240,7 @@ struct Region {
 
     // Sound source: sample playback
     FileId sampleId {}; // Sample
+    int sampleQuality { Default::sampleQuality };
     float delay { Default::delay }; // delay
     float delayRandom { Default::delayRandom }; // delay_random
     int64_t offset { Default::offset }; // offset

src/sfizz/Voice.cpp

@@ -506,23 +506,25 @@ void sfz::Voice::fillWithData(AudioSpan<float> buffer) noexcept
         }
     }
 
-    auto ind = indices->data();
-    auto coeff = coeffs->data();
-    auto leftSource = source.getConstSpan(0);
-    auto left = buffer.getChannel(0);
-    if (source.getNumChannels() == 1) {
-        while (ind < indices->end()) {
-            *left = interpolate<kInterpolatorBspline3>(&leftSource[*ind], *coeff);
-            incrementAll(ind, left, coeff);
-        }
-    } else {
-        auto right = buffer.getChannel(1);
-        auto rightSource = source.getConstSpan(1);
-        while (ind < indices->end()) {
-            *left = interpolate<kInterpolatorBspline3>(&leftSource[*ind], *coeff);
-            *right = interpolate<kInterpolatorBspline3>(&rightSource[*ind], *coeff);
-            incrementAll(ind, left, right, coeff);
-        }
+    const int quality = region->sampleQuality;
+
+    switch (quality) {
+    default:
+        if (quality > 2)
+            goto high; // TODO sinc, not implemented
+        // fall through
+    case 1:
+        fillInterpolated<kInterpolatorLinear>(source, buffer, *indices, *coeffs);
+        break;
+    case 2: high:
+#if 1
+        // B-spline response has faster decay of aliasing, but not zero-crossings at integer positions
+        fillInterpolated<kInterpolatorBspline3>(source, buffer, *indices, *coeffs);
+#else
+        // Hermite polynomial
+        fillInterpolated<kInterpolatorHermite3>(source, buffer, *indices, *coeffs);
+#endif
+        break;
     }
 
     sourcePosition = indices->back();
@@ -536,6 +538,31 @@ void sfz::Voice::fillWithData(AudioSpan<float> buffer) noexcept
 #endif
 }
 
+template <sfz::InterpolatorModel M>
+void sfz::Voice::fillInterpolated(
+    const sfz::AudioSpan<const float>& source, sfz::AudioSpan<float>& dest,
+    absl::Span<const int> indices, absl::Span<const float> coeffs)
+{
+    auto ind = indices.data();
+    auto coeff = coeffs.data();
+    auto leftSource = source.getConstSpan(0);
+    auto left = dest.getChannel(0);
+    if (source.getNumChannels() == 1) {
+        while (ind < indices.end()) {
+            *left = sfz::interpolate<M>(&leftSource[*ind], *coeff);
+            incrementAll(ind, left, coeff);
+        }
+    } else {
+        auto right = dest.getChannel(1);
+        auto rightSource = source.getConstSpan(1);
+        while (ind < indices.end()) {
+            *left = sfz::interpolate<M>(&leftSource[*ind], *coeff);
+            *right = sfz::interpolate<M>(&rightSource[*ind], *coeff);
+            incrementAll(ind, left, right, coeff);
+        }
+    }
+}
+
 void sfz::Voice::fillWithGenerator(AudioSpan<float> buffer) noexcept
 {
     const auto leftSpan = buffer.getSpan(0);

src/sfizz/Voice.h

@@ -19,6 +19,7 @@
 #include <random>
 
 namespace sfz {
+enum InterpolatorModel : int;
 /**
  * @brief The SFZ voice are the polyphony holders. They get activated by the synth
  * and tasked to play a given region until the end, stopping on note-offs, off-groups
@@ -242,6 +243,20 @@ private:
      * @param buffer
      */
     void fillWithGenerator(AudioSpan<float> buffer) noexcept;
+
+    /**
+     * @brief Fill a destination with an interpolated source.
+     *
+     * @param source the source sample
+     * @param dest the destination buffer
+     * @param indices the integral parts of the source positions
+     * @param coeffs the fractional parts of the source positions
+     */
+    template <sfz::InterpolatorModel M>
+    static void fillInterpolated(
+        const sfz::AudioSpan<const float>& source, sfz::AudioSpan<float>& dest,
+        absl::Span<const int> indices, absl::Span<const float> coeffs);
+
     void amplitudeEnvelope(absl::Span<float> modulationSpan) noexcept;
     void ampStageMono(AudioSpan<float> buffer) noexcept;
     void ampStageStereo(AudioSpan<float> buffer) noexcept;