Add excessFileFrames at the beginning of the file dataRecenter the 4-sample splines from -1 to 2 (relative to the interpolated sample) rather than 0 to 3

src/sfizz/FilePool.cpp

@@ -27,6 +27,7 @@
 #include "FileInstrument.h"
 #include "Buffer.h"
 #include "AudioBuffer.h"
+#include "AudioSpan.h"
 #include "Config.h"
 #include "Debug.h"
 #include "Oversampler.h"
@@ -42,7 +43,7 @@ template <class T>
 void readBaseFile(SndfileHandle& sndFile, sfz::AudioBuffer<T>& output, uint32_t numFrames, bool reverse)
 {
     output.reset();
-    output.resize(numFrames + sfz::config::excessFileFrames);
+    output.resize(numFrames + 2 * sfz::config::excessFileFrames);
 
     if (reverse)
         sndFile.seek(-static_cast<sf_count_t>(numFrames), SEEK_END);
@@ -52,20 +53,23 @@ void readBaseFile(SndfileHandle& sndFile, sfz::AudioBuffer<T>& output, uint32_t
     if (channels == 1) {
         output.addChannel();
         output.clear();
-        sndFile.readf(output.channelWriter(0), numFrames);
+        sndFile.readf(output.channelWriter(0) + sfz::config::excessFileFrames, numFrames);
     } else if (channels == 2) {
         output.addChannel();
         output.addChannel();
         output.clear();
         sfz::Buffer<T> tempReadBuffer { 2 * numFrames };
         sndFile.readf(tempReadBuffer.data(), numFrames);
-        sfz::readInterleaved<T>(tempReadBuffer, output.getSpan(0).first(numFrames), output.getSpan(1).first(numFrames));
+        sfz::readInterleaved<T>(tempReadBuffer,
+            output.getSpan(0).subspan(sfz::config::excessFileFrames, numFrames),
+            output.getSpan(1).subspan(sfz::config::excessFileFrames, numFrames)
+        );
     }
 
     if (reverse) {
         for (unsigned c = 0; c < channels; ++c) {
             // TODO: consider optimizing with SIMD
-            absl::Span<float> channel = output.getSpan(c).first(numFrames);
+            absl::Span<float> channel = output.getSpan(c).subspan(sfz::config::excessFileFrames, numFrames);
             std::reverse(channel.begin(), channel.end());
         }
     }
@@ -80,10 +84,12 @@ std::unique_ptr<sfz::AudioBuffer<T>> readFromFile(SndfileHandle& sndFile, uint32
     if (factor == sfz::Oversampling::x1)
         return baseBuffer;
 
-    auto outputBuffer = absl::make_unique<sfz::AudioBuffer<T>>(sndFile.channels(), numFrames * static_cast<int>(factor) + sfz::config::excessFileFrames);
+    auto outputBuffer = absl::make_unique<sfz::AudioBuffer<T>>(sndFile.channels(), numFrames * static_cast<int>(factor) + 2 * sfz::config::excessFileFrames);
     outputBuffer->clear();
+    auto baseSpan = sfz::AudioSpan<T>(*baseBuffer).subspan(sfz::config::excessFileFrames, numFrames);
+    auto outputSpan = sfz::AudioSpan<T>(*outputBuffer).subspan(sfz::config::excessFileFrames, numFrames * static_cast<int>(factor));
     sfz::Oversampler oversampler { factor };
-    oversampler.stream(*baseBuffer, *outputBuffer);
+    oversampler.stream(baseSpan, outputSpan);
     return outputBuffer;
 }
 
@@ -100,10 +106,12 @@ void streamFromFile(SndfileHandle& sndFile, uint32_t numFrames, sfz::Oversamplin
     auto baseBuffer = readFromFile<T>(sndFile, numFrames, sfz::Oversampling::x1, reverse);
     output.reset();
     output.addChannels(baseBuffer->getNumChannels());
-    output.resize(numFrames * static_cast<int>(factor) + sfz::config::excessFileFrames);
+    output.resize(numFrames * static_cast<int>(factor) + 2 * sfz::config::excessFileFrames);
     output.clear();
     sfz::Oversampler oversampler { factor };
-    oversampler.stream(*baseBuffer, output, filledFrames);
+    auto baseSpan = sfz::AudioSpan<T>(*baseBuffer).subspan(sfz::config::excessFileFrames, numFrames);
+    auto outputSpan = sfz::AudioSpan<T>(output).subspan(sfz::config::excessFileFrames, numFrames * static_cast<int>(factor));
+    oversampler.stream(baseSpan, outputSpan, filledFrames);
 }
 
 sfz::FilePool::FilePool(sfz::Logger& logger)

src/sfizz/FilePool.h

@@ -66,11 +66,14 @@ struct FilePromise
     {
         if (dataStatus == DataStatus::Ready)
             return AudioSpan<const float>(fileData)
-                .first(fileData.getNumFrames() - sfz::config::excessFileFrames);
+                .subspan(sfz::config::excessFileFrames,
+                    fileData.getNumFrames() - 2 * sfz::config::excessFileFrames);
         else if (availableFrames > preloadedData->getNumFrames())
-            return AudioSpan<const float>(fileData).first(availableFrames);
+            return AudioSpan<const float>(fileData).subspan(sfz::config::excessFileFrames, availableFrames);
         else
-            return AudioSpan<const float>(*preloadedData);
+            return AudioSpan<const float>(*preloadedData)
+                .subspan(sfz::config::excessFileFrames,
+                    preloadedData->getNumFrames() - sfz::config::excessFileFrames);
     }
 
     void reset()

src/sfizz/Interpolators.h

@@ -17,6 +17,19 @@ enum InterpolatorModel : int {
     kInterpolatorBspline3,
 };
 
+/**
+ * @brief Interpolate from a vector of values
+ *
+ * @tparam M the interpolator model
+ * @tparam R the sample type
+ * @param values Pointer to a value in a larger vector of values.
+ *               Depending on the interpolator the algorithm may
+ *               read samples before and after. Usually you need
+ *               to ensure that you have order - 1 samples available
+ *               before and after the pointer, padding if necessary.
+ * @param coeff the interpolation coefficient
+ * @return R
+ */
 template <InterpolatorModel M, class R>
 R interpolate(const R* values, R coeff);
 

src/sfizz/Interpolators.hpp

@@ -44,7 +44,7 @@ public:
     {
         __m128 x = _mm_sub_ps(_mm_setr_ps(-1, 0, 1, 2), _mm_set1_ps(coeff));
         __m128 h = hermite3x4(x);
-        __m128 y = _mm_mul_ps(h, _mm_loadu_ps(values));
+        __m128 y = _mm_mul_ps(h, _mm_loadu_ps(values - 1));
         // sum 4 to 1
         __m128 xmm0 = y;
         __m128 xmm1 = _mm_shuffle_ps(xmm0, xmm0, 0xe5);
@@ -68,8 +68,8 @@ public:
     static inline R process(const R* values, R coeff)
     {
         R y = 0;
-        for (int i = 0; i < 4; ++i) {
+        for (int i = -1; i < 3; ++i) {
-            R h = hermite3<R>(i - 1 - coeff);
+            R h = hermite3<R>(i - coeff);
             y += h * values[i];
         }
         return y;
@@ -88,7 +88,7 @@ public:
     {
         __m128 x = _mm_sub_ps(_mm_setr_ps(-1, 0, 1, 2), _mm_set1_ps(coeff));
         __m128 h = bspline3x4(x);
-        __m128 y = _mm_mul_ps(h, _mm_loadu_ps(values));
+        __m128 y = _mm_mul_ps(h, _mm_loadu_ps(values - 1));
         // sum 4 to 1
         __m128 xmm0 = y;
         __m128 xmm1 = _mm_shuffle_ps(xmm0, xmm0, 0xe5);
@@ -112,8 +112,8 @@ public:
     static inline R process(const R* values, R coeff)
     {
         R y = 0;
-        for (int i = 0; i < 4; ++i) {
+        for (int i = -1; i < 3; ++i) {
-            R h = bspline3<R>(i - 1 - coeff);
+            R h = bspline3<R>(i - coeff);
             y += h * values[i];
         }
         return y;

src/sfizz/Oversampler.cpp

@@ -61,7 +61,7 @@ sfz::Oversampler::Oversampler(sfz::Oversampling factor, size_t chunkSize)
 
 }
 
-void sfz::Oversampler::stream(const sfz::AudioBuffer<float>& input, sfz::AudioBuffer<float>& output, std::atomic<size_t>* framesReady)
+void sfz::Oversampler::stream(AudioSpan<float> input, AudioSpan<float> output, std::atomic<size_t>* framesReady)
 {
     ASSERT(output.getNumFrames() >= input.getNumFrames() * static_cast<int>(factor));
     ASSERT(output.getNumChannels() == input.getNumChannels());

src/sfizz/Oversampler.h

@@ -11,6 +11,7 @@
 #include "Debug.h"
 #include "Buffer.h"
 #include "AudioBuffer.h"
+#include "AudioSpan.h"
 #include "Config.h"
 
 namespace sfz {
@@ -39,7 +40,7 @@ public:
      * @param output
      * @param framesReady an atomic counter for the ready frames. If null no signaling is done.
      */
-    void stream(const AudioBuffer<float>& input, AudioBuffer<float>& output, std::atomic<size_t>* framesReady = nullptr);
+    void stream(AudioSpan<float> input, AudioSpan<float> output, std::atomic<size_t>* framesReady = nullptr);
 
     Oversampler() = delete;
     Oversampler(const Oversampler&) = delete;