ebiten/audio/internal/oboe/oboe_flowgraph_resampler_PolyphaseResamplerMono_android.cpp

64 lines
2.1 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 "oboe_flowgraph_resampler_PolyphaseResamplerMono_android.h"
using namespace resampler;
#define MONO 1
PolyphaseResamplerMono::PolyphaseResamplerMono(const MultiChannelResampler::Builder &builder)
: PolyphaseResampler(builder) {
assert(builder.getChannelCount() == MONO);
}
void PolyphaseResamplerMono::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 * MONO];
const int offset = mNumTaps * MONO;
// Write each channel twice so we avoid having to wrap when running the FIR.
const float sample = frame[0];
// Put ordered writes together.
dest[0] = sample;
dest[offset] = sample;
}
void PolyphaseResamplerMono::readFrame(float *frame) {
// Clear accumulator.
float sum = 0.0;
// Multiply input times precomputed windowed sinc function.
const float *coefficients = &mCoefficients[mCoefficientCursor];
float *xFrame = &mX[mCursor * MONO];
const int numLoops = mNumTaps >> 2; // n/4
for (int i = 0; i < numLoops; i++) {
// Manual loop unrolling, might get converted to SIMD.
sum += *xFrame++ * *coefficients++;
sum += *xFrame++ * *coefficients++;
sum += *xFrame++ * *coefficients++;
sum += *xFrame++ * *coefficients++;
}
mCoefficientCursor = (mCoefficientCursor + mNumTaps) % mCoefficients.size();
// Copy accumulator to output.
frame[0] = sum;
}