1 /* 2 ** 3 ** Copyright 2009, The Android Open Source Project 4 ** 5 ** Licensed under the Apache License, Version 2.0 (the "License"); 6 ** you may not use this file except in compliance with the License. 7 ** You may obtain a copy of the License at 8 ** 9 ** http://www.apache.org/licenses/LICENSE-2.0 10 ** 11 ** Unless required by applicable law or agreed to in writing, software 12 ** distributed under the License is distributed on an "AS IS" BASIS, 13 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 ** See the License for the specific language governing permissions and 15 ** limitations under the License. 16 */ 17 18 #ifndef ANDROID_AUDIO_COMMON_H 19 #define ANDROID_AUDIO_COMMON_H 20 21 #include <stdint.h> 22 #include <stddef.h> 23 24 namespace android { 25 26 // Audio coefficient type. 27 typedef int32_t audio_coef_t; 28 // Audio sample type. 29 typedef int32_t audio_sample_t; 30 // Accumulator type for coef x sample. 31 typedef int64_t audio_coef_sample_acc_t; 32 33 // Number of fraction bits for audio coefficient. 34 static const int AUDIO_COEF_PRECISION = 24; 35 // Audio coefficient with the value of 1.0 36 static const audio_coef_t AUDIO_COEF_ONE = 1 << AUDIO_COEF_PRECISION; 37 // Audio coefficient with the value of 0.5 38 static const audio_coef_t AUDIO_COEF_HALF = 1 << (AUDIO_COEF_PRECISION - 1); 39 // Number of fraction bits for audio sample. 40 static const int AUDIO_SAMPLE_PRECISION = 24; 41 // Audio sample with the value of 1.0 42 static const audio_sample_t AUDIO_SAMPLE_ONE = 1 << AUDIO_SAMPLE_PRECISION; 43 44 // TODO: These are just temporary naive implementations of the necessary 45 // arithmetic operations needed for the filter. They should be moved to a more 46 // generic location and implemented more efficiently. 47 48 // Multiply a sample by a coefficient to return an accumulator. 49 inline audio_coef_sample_acc_t mul_coef_sample(audio_coef_t x, audio_sample_t y) { 50 return ((audio_coef_sample_acc_t) (x)) * y; 51 } 52 53 // Multiply and accumulate sample by a coefficient to return an accumulator. 54 inline audio_coef_sample_acc_t mac_coef_sample(audio_coef_t x, audio_sample_t y, audio_coef_sample_acc_t acc) { 55 return acc + ((audio_coef_sample_acc_t) (x)) * y; 56 } 57 58 // Convert a sample-coefficient accumulator to a sample. 59 inline audio_sample_t coef_sample_acc_to_sample(audio_coef_sample_acc_t acc) { 60 if (acc < 0) { 61 acc += AUDIO_COEF_ONE - 1; 62 } 63 return (audio_sample_t) (acc >> AUDIO_COEF_PRECISION); 64 } 65 66 // Convert a S15 sample to audio_sample_t 67 inline audio_sample_t s15_to_audio_sample_t(int16_t s15) { 68 return audio_sample_t(s15) << 9; 69 } 70 71 // Convert a audio_sample_t sample to S15 (no clipping) 72 inline int16_t audio_sample_t_to_s15(audio_sample_t sample) { 73 return int16_t((sample + (1 << 8)) >> 9); 74 } 75 76 // Convert a audio_sample_t sample to S15 (with clipping) 77 inline int16_t audio_sample_t_to_s15_clip(audio_sample_t sample) { 78 // TODO: optimize for targets supporting this as an atomic operation. 79 if (__builtin_expect(sample >= (0x7FFF << 9), 0)) { 80 return 0x7FFF; 81 } else if (__builtin_expect(sample <= -(0x8000 << 9), 0)) { 82 return 0x8000; 83 } else { 84 return audio_sample_t_to_s15(sample); 85 } 86 } 87 88 //////////////////////////////////////////////////////////////////////////////// 89 90 } 91 92 #endif // ANDROID_AUDIO_COMMON_H 93
