1 files changed, 79 insertions, 0 deletions
diff --git a/externals/oboe/src/flowgraph/resampler/PolyphaseResamplerStereo.cpp b/externals/oboe/src/flowgraph/resampler/PolyphaseResamplerStereo.cpp
new file mode 100644
index 0000000000..b38185186a
--- /dev/null
+++ b/externals/oboe/src/flowgraph/resampler/PolyphaseResamplerStereo.cpp
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <cassert>
+#include "PolyphaseResamplerStereo.h"
+
+using namespace RESAMPLER_OUTER_NAMESPACE::resampler;
+
+#define STEREO  2
+
+PolyphaseResamplerStereo::PolyphaseResamplerStereo(const MultiChannelResampler::Builder &builder)
+        : PolyphaseResampler(builder) {
+    assert(builder.getChannelCount() == STEREO);
+}
+
+void PolyphaseResamplerStereo::writeFrame(const float *frame) {
+    // Move cursor before write so that cursor points to last written frame in read.
+    if (--mCursor < 0) {
+        mCursor = getNumTaps() - 1;
+    }
+    float *dest = &mX[mCursor * STEREO];
+    const int offset = mNumTaps * STEREO;
+    // Write each channel twice so we avoid having to wrap when running the FIR.
+    const float left =  frame[0];
+    const float right = frame[1];
+    // Put ordered writes together.
+    dest[0] = left;
+    dest[1] = right;
+    dest[offset] = left;
+    dest[1 + offset] = right;
+}
+
+void PolyphaseResamplerStereo::readFrame(float *frame) {
+    // Clear accumulators.
+    float left = 0.0;
+    float right = 0.0;
+
+    // Multiply input times precomputed windowed sinc function.
+    const float *coefficients = &mCoefficients[mCoefficientCursor];
+    float *xFrame = &mX[mCursor * STEREO];
+    const int numLoops = mNumTaps >> 2; // n/4
+    for (int i = 0; i < numLoops; i++) {
+        // Manual loop unrolling, might get converted to SIMD.
+        float coefficient = *coefficients++;
+        left += *xFrame++ * coefficient;
+        right += *xFrame++ * coefficient;
+
+        coefficient = *coefficients++; // next tap
+        left += *xFrame++ * coefficient;
+        right += *xFrame++ * coefficient;
+
+        coefficient = *coefficients++;  // next tap
+        left += *xFrame++ * coefficient;
+        right += *xFrame++ * coefficient;
+
+        coefficient = *coefficients++;  // next tap
+        left += *xFrame++ * coefficient;
+        right += *xFrame++ * coefficient;
+    }
+
+    mCoefficientCursor = (mCoefficientCursor + mNumTaps) % mCoefficients.size();
+
+    // Copy accumulators to output.
+    frame[0] = left;
+    frame[1] = right;
+}