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/*
* 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 <math.h>
#include "SincResamplerStereo.h"
using namespace RESAMPLER_OUTER_NAMESPACE::resampler;
#define STEREO 2
SincResamplerStereo::SincResamplerStereo(const MultiChannelResampler::Builder &builder)
: SincResampler(builder) {
assert(builder.getChannelCount() == STEREO);
}
void SincResamplerStereo::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;
}
// Multiply input times windowed sinc function.
void SincResamplerStereo::readFrame(float *frame) {
// Clear accumulator for mixing.
std::fill(mSingleFrame.begin(), mSingleFrame.end(), 0.0);
std::fill(mSingleFrame2.begin(), mSingleFrame2.end(), 0.0);
// Determine indices into coefficients table.
double tablePhase = getIntegerPhase() * mPhaseScaler;
int index1 = static_cast<int>(floor(tablePhase));
float *coefficients1 = &mCoefficients[static_cast<size_t>(index1)
* static_cast<size_t>(getNumTaps())];
int index2 = (index1 + 1);
float *coefficients2 = &mCoefficients[static_cast<size_t>(index2)
* static_cast<size_t>(getNumTaps())];
float *xFrame = &mX[static_cast<size_t>(mCursor) * static_cast<size_t>(getChannelCount())];
for (int i = 0; i < mNumTaps; i++) {
float coefficient1 = *coefficients1++;
float coefficient2 = *coefficients2++;
for (int channel = 0; channel < getChannelCount(); channel++) {
float sample = *xFrame++;
mSingleFrame[channel] += sample * coefficient1;
mSingleFrame2[channel] += sample * coefficient2;
}
}
// Interpolate and copy to output.
float fraction = tablePhase - index1;
for (int channel = 0; channel < getChannelCount(); channel++) {
float low = mSingleFrame[channel];
float high = mSingleFrame2[channel];
frame[channel] = low + (fraction * (high - low));
}
}
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