1 /*
2 * Copyright 2019 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <math.h>
18 #include "SincResampler.h"
19
20 using namespace resampler;
21
SincResampler(const MultiChannelResampler::Builder & builder)22 SincResampler::SincResampler(const MultiChannelResampler::Builder &builder)
23 : MultiChannelResampler(builder)
24 , mSingleFrame2(builder.getChannelCount()) {
25 assert((getNumTaps() % 4) == 0); // Required for loop unrolling.
26 mNumRows = kMaxCoefficients / getNumTaps(); // no guard row needed
27 // printf("SincResampler: numRows = %d\n", mNumRows);
28 mPhaseScaler = (double) mNumRows / mDenominator;
29 double phaseIncrement = 1.0 / mNumRows;
30 generateCoefficients(builder.getInputRate(),
31 builder.getOutputRate(),
32 mNumRows,
33 phaseIncrement,
34 builder.getNormalizedCutoff());
35 }
36
readFrame(float * frame)37 void SincResampler::readFrame(float *frame) {
38 // Clear accumulator for mixing.
39 std::fill(mSingleFrame.begin(), mSingleFrame.end(), 0.0);
40 std::fill(mSingleFrame2.begin(), mSingleFrame2.end(), 0.0);
41
42 // Determine indices into coefficients table.
43 double tablePhase = getIntegerPhase() * mPhaseScaler;
44 int index1 = static_cast<int>(floor(tablePhase));
45 if (index1 >= mNumRows) { // no guard row needed because we wrap the indices
46 tablePhase -= mNumRows;
47 index1 -= mNumRows;
48 }
49
50 int index2 = index1 + 1;
51 if (index2 >= mNumRows) { // no guard row needed because we wrap the indices
52 index2 -= mNumRows;
53 }
54
55 float *coefficients1 = &mCoefficients[index1 * getNumTaps()];
56 float *coefficients2 = &mCoefficients[index2 * getNumTaps()];
57
58 float *xFrame = &mX[mCursor * getChannelCount()];
59 for (int i = 0; i < mNumTaps; i++) {
60 float coefficient1 = *coefficients1++;
61 float coefficient2 = *coefficients2++;
62 for (int channel = 0; channel < getChannelCount(); channel++) {
63 float sample = *xFrame++;
64 mSingleFrame[channel] += sample * coefficient1;
65 mSingleFrame2[channel] += sample * coefficient2;
66 }
67 }
68
69 // Interpolate and copy to output.
70 float fraction = tablePhase - index1;
71 for (int channel = 0; channel < getChannelCount(); channel++) {
72 float low = mSingleFrame[channel];
73 float high = mSingleFrame2[channel];
74 frame[channel] = low + (fraction * (high - low));
75 }
76 }
77