| /* |
| * Copyright (C) 2020 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 <string.h> |
| #include <math.h> |
| #include "audio_ops.h" |
| |
| namespace android { |
| namespace hardware { |
| namespace audio { |
| namespace V7_0 { |
| namespace implementation { |
| namespace aops { |
| |
| void multiplyByVolume(const float volume, int16_t *a, const size_t n) { |
| constexpr int_fast32_t kDenominator = 32768; |
| const int_fast32_t numerator = |
| static_cast<int_fast32_t>(round(volume * kDenominator)); |
| |
| if (numerator >= kDenominator) { |
| return; // (numerator > kDenominator) is not expected |
| } else if (numerator <= 0) { |
| memset(a, 0, n * sizeof(*a)); |
| return; // (numerator < 0) is not expected |
| } |
| |
| int16_t *end = a + n; |
| |
| // The unroll code below is to save on CPU branch instructions. |
| // 8 is arbitrary chosen. |
| |
| #define STEP \ |
| *a = (*a * numerator + kDenominator / 2) / kDenominator; \ |
| ++a |
| |
| switch (n % 8) { |
| case 7: goto l7; |
| case 6: goto l6; |
| case 5: goto l5; |
| case 4: goto l4; |
| case 3: goto l3; |
| case 2: goto l2; |
| case 1: goto l1; |
| default: break; |
| } |
| |
| while (a < end) { |
| STEP; |
| l7: STEP; |
| l6: STEP; |
| l5: STEP; |
| l4: STEP; |
| l3: STEP; |
| l2: STEP; |
| l1: STEP; |
| } |
| |
| #undef STEP |
| } |
| |
| } // namespace aops |
| } // namespace implementation |
| } // namespace V7_0 |
| } // namespace audio |
| } // namespace hardware |
| } // namespace android |