80 lines
1.9 KiB
C++
80 lines
1.9 KiB
C++
/*
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* Copyright (C) 2020 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <string.h>
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#include <math.h>
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#include "audio_ops.h"
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namespace android {
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namespace hardware {
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namespace audio {
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namespace CPP_VERSION {
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namespace implementation {
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namespace aops {
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void multiplyByVolume(const float volume, int16_t *a, const size_t n) {
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constexpr int_fast32_t kDenominator = 32768;
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const int_fast32_t numerator =
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static_cast<int_fast32_t>(round(volume * kDenominator));
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if (numerator >= kDenominator) {
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return; // (numerator > kDenominator) is not expected
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} else if (numerator <= 0) {
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memset(a, 0, n * sizeof(*a));
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return; // (numerator < 0) is not expected
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}
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int16_t *end = a + n;
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// The unroll code below is to save on CPU branch instructions.
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// 8 is arbitrary chosen.
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#define STEP \
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*a = (*a * numerator + kDenominator / 2) / kDenominator; \
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++a
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switch (n % 8) {
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case 7: goto l7;
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case 6: goto l6;
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case 5: goto l5;
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case 4: goto l4;
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case 3: goto l3;
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case 2: goto l2;
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case 1: goto l1;
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default: break;
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}
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while (a < end) {
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STEP;
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l7: STEP;
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l6: STEP;
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l5: STEP;
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l4: STEP;
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l3: STEP;
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l2: STEP;
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l1: STEP;
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}
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#undef STEP
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}
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} // namespace aops
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} // namespace implementation
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} // namespace CPP_VERSION
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} // namespace audio
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} // namespace hardware
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} // namespace android
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