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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 "IntegerRatio.h"
#include "PolyphaseResampler.h"
using namespace resampler;
PolyphaseResampler::PolyphaseResampler(const MultiChannelResampler::Builder &builder)
: MultiChannelResampler(builder)
{
assert((getNumTaps() % 4) == 0); // Required for loop unrolling.
int32_t inputRate = builder.getInputRate();
int32_t outputRate = builder.getOutputRate();
int32_t numRows = mDenominator;
double phaseIncrement = (double) inputRate / (double) outputRate;
generateCoefficients(inputRate, outputRate,
numRows, phaseIncrement,
builder.getNormalizedCutoff());
}
void PolyphaseResampler::readFrame(float *frame) {
// Clear accumulator for mixing.
std::fill(mSingleFrame.begin(), mSingleFrame.end(), 0.0);
// printf("PolyphaseResampler: mCoefficientCursor = %4d\n", mCoefficientCursor);
// Multiply input times windowed sinc function.
float *coefficients = &mCoefficients[mCoefficientCursor];
float *xFrame = &mX[mCursor * getChannelCount()];
for (int i = 0; i < mNumTaps; i++) {
float coefficient = *coefficients++;
// printf("PolyphaseResampler: coeff = %10.6f, xFrame[0] = %10.6f\n", coefficient, xFrame[0]);
for (int channel = 0; channel < getChannelCount(); channel++) {
mSingleFrame[channel] += *xFrame++ * coefficient;
}
}
// Advance and wrap through coefficients.
mCoefficientCursor = (mCoefficientCursor + mNumTaps) % mCoefficients.size();
// Copy accumulator to output.
for (int channel = 0; channel < getChannelCount(); channel++) {
frame[channel] = mSingleFrame[channel];
}
}
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