ebiten/audio/internal/oboe/oboe_flowgraph_resampler_SincResampler_android.cpp

78 lines
2.9 KiB
C++
Vendored

/*
* 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 "oboe_flowgraph_resampler_SincResampler_android.h"
using namespace resampler;
SincResampler::SincResampler(const MultiChannelResampler::Builder &builder)
: MultiChannelResampler(builder)
, mSingleFrame2(builder.getChannelCount()) {
assert((getNumTaps() % 4) == 0); // Required for loop unrolling.
mNumRows = kMaxCoefficients / getNumTaps(); // no guard row needed
// printf("SincResampler: numRows = %d\n", mNumRows);
mPhaseScaler = (double) mNumRows / mDenominator;
double phaseIncrement = 1.0 / mNumRows;
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.
double tablePhase = getIntegerPhase() * mPhaseScaler;
int index1 = static_cast<int>(floor(tablePhase));
if (index1 >= mNumRows) { // no guard row needed because we wrap the indices
tablePhase -= mNumRows;
index1 -= mNumRows;
}
int index2 = index1 + 1;
if (index2 >= mNumRows) { // no guard row needed because we wrap the indices
index2 -= mNumRows;
}
float *coefficients1 = &mCoefficients[index1 * getNumTaps()];
float *coefficients2 = &mCoefficients[index2 * getNumTaps()];
float *xFrame = &mX[mCursor * 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));
}
}