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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 <algorithm> // Do NOT delete. Needed for LLVM. See #1746
#include <cassert>
#include <math.h>
#include "SincResampler.h"
using namespace RESAMPLER_OUTER_NAMESPACE::resampler;
SincResampler::SincResampler(const MultiChannelResampler::Builder &builder)
: MultiChannelResampler(builder)
, mSingleFrame2(builder.getChannelCount()) {
assert((getNumTaps() % 4) == 0); // Required for loop unrolling.
mNumRows = kMaxCoefficients / getNumTaps(); // includes guard row
const int32_t numRowsNoGuard = mNumRows - 1;
mPhaseScaler = (double) numRowsNoGuard / mDenominator;
const double phaseIncrement = 1.0 / numRowsNoGuard;
generateCoefficients(builder.getInputRate(),
builder.getOutputRate(),
mNumRows,
phaseIncrement,
builder.getNormalizedCutoff());
}
void SincResampler::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.
const double tablePhase = getIntegerPhase() * mPhaseScaler;
const int indexLow = static_cast<int>(floor(tablePhase));
const int indexHigh = indexLow + 1; // OK because using a guard row.
assert (indexHigh < mNumRows);
float *coefficientsLow = &mCoefficients[static_cast<size_t>(indexLow)
* static_cast<size_t>(getNumTaps())];
float *coefficientsHigh = &mCoefficients[static_cast<size_t>(indexHigh)
* static_cast<size_t>(getNumTaps())];
float *xFrame = &mX[static_cast<size_t>(mCursor) * static_cast<size_t>(getChannelCount())];
for (int tap = 0; tap < mNumTaps; tap++) {
const float coefficientLow = *coefficientsLow++;
const float coefficientHigh = *coefficientsHigh++;
for (int channel = 0; channel < getChannelCount(); channel++) {
const float sample = *xFrame++;
mSingleFrame[channel] += sample * coefficientLow;
mSingleFrame2[channel] += sample * coefficientHigh;
}
}
// Interpolate and copy to output.
const float fraction = tablePhase - indexLow;
for (int channel = 0; channel < getChannelCount(); channel++) {
const float low = mSingleFrame[channel];
const float high = mSingleFrame2[channel];
frame[channel] = low + (fraction * (high - low));
}
}
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