From 3cd56b4697d27c43b48ff3bb8ecfc12576219c28 Mon Sep 17 00:00:00 2001
From: Jean Pierre Cimalando <jp-dev@inbox.ru>
Date: Mon, 22 Jun 2020 06:39:06 +0200
Subject: [PATCH] Support interpolation to nearest

---
 src/sfizz/Interpolators.h   |  2 ++
 src/sfizz/Interpolators.hpp | 13 +++++++++++++
 src/sfizz/Wavetables.cpp    | 10 ++++++----
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/src/sfizz/Interpolators.h b/src/sfizz/Interpolators.h
index f784eefd..c4fdbbd9 100644
--- a/src/sfizz/Interpolators.h
+++ b/src/sfizz/Interpolators.h
@@ -9,6 +9,8 @@
 namespace sfz {
 
 enum InterpolatorModel : int {
+    // a nearest interpolator
+    kInterpolatorNearest,
     // a linear interpolator
     kInterpolatorLinear,
     // a Hermite 3rd order interpolator
diff --git a/src/sfizz/Interpolators.hpp b/src/sfizz/Interpolators.hpp
index 1f462578..5c302900 100644
--- a/src/sfizz/Interpolators.hpp
+++ b/src/sfizz/Interpolators.hpp
@@ -19,6 +19,19 @@ inline R interpolate(const R* values, R coeff)
     return Interpolator<M, R>::process(values, coeff);
 }
 
+//------------------------------------------------------------------------------
+// Nearest
+
+template <class R>
+class Interpolator<kInterpolatorNearest, R>
+{
+public:
+    static inline R process(const R* values, R coeff)
+    {
+        return values[coeff > static_cast<R>(0.5)];
+    }
+};
+
 //------------------------------------------------------------------------------
 // Linear
 
diff --git a/src/sfizz/Wavetables.cpp b/src/sfizz/Wavetables.cpp
index 929735a1..e294cfee 100644
--- a/src/sfizz/Wavetables.cpp
+++ b/src/sfizz/Wavetables.cpp
@@ -144,8 +144,9 @@ void WavetableOscillator::process(float frequency, float detuneRatio, float* out
     int quality = clamp(_quality, 0, 3);
 
     switch (quality) {
-    case 0: // supposed to be nearest according to book
-        // fall through
+    case 0:
+        processSingle<kInterpolatorNearest>(frequency, detuneRatio, output, nframes);
+        break;
     case 1:
         processSingle<kInterpolatorLinear>(frequency, detuneRatio, output, nframes);
         break;
@@ -163,8 +164,9 @@ void WavetableOscillator::processModulated(const float* frequencies, float detun
     int quality = clamp(_quality, 0, 3);
 
     switch (quality) {
-    case 0: // supposed to be nearest according to book
-        // fall through
+    case 0:
+        processModulatedSingle<kInterpolatorNearest>(frequencies, detuneRatio, output, nframes);
+        break;
     case 1:
         processModulatedSingle<kInterpolatorLinear>(frequencies, detuneRatio, output, nframes);
         break;