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#include <cutils/compiler.h>
24
25namespace android {
26
27// Audio coefficient type.
28typedef int32_t audio_coef_t;
29// Audio sample type.
30typedef int32_t audio_sample_t;
31// Accumulator type for coef x sample.
32typedef int64_t audio_coef_sample_acc_t;
33
34// Number of fraction bits for audio coefficient.
35static const int AUDIO_COEF_PRECISION = 24;
36// Audio coefficient with the value of 1.0
37static const audio_coef_t AUDIO_COEF_ONE = 1 << AUDIO_COEF_PRECISION;
38// Audio coefficient with the value of 0.5
39static const audio_coef_t AUDIO_COEF_HALF = 1 << (AUDIO_COEF_PRECISION - 1);
40// Number of fraction bits for audio sample.
41static const int AUDIO_SAMPLE_PRECISION = 24;
42// Audio sample with the value of 1.0
43static const audio_sample_t AUDIO_SAMPLE_ONE = 1 << AUDIO_SAMPLE_PRECISION;
44
45// TODO: These are just temporary naive implementations of the necessary
46// arithmetic operations needed for the filter. They should be moved to a more
47// generic location and implemented more efficiently.
48
49// Multiply a sample by a coefficient to return an accumulator.
50inline audio_coef_sample_acc_t mul_coef_sample(audio_coef_t x, audio_sample_t y) {
51    return ((audio_coef_sample_acc_t) (x)) * y;
52}
53
54// Multiply and accumulate sample by a coefficient to return an accumulator.
55inline audio_coef_sample_acc_t mac_coef_sample(audio_coef_t x, audio_sample_t y, audio_coef_sample_acc_t acc) {
56    return acc + ((audio_coef_sample_acc_t) (x)) * y;
57}
58
59// Convert a sample-coefficient accumulator to a sample.
60inline audio_sample_t coef_sample_acc_to_sample(audio_coef_sample_acc_t acc) {
61    if (acc < 0) {
62        acc += AUDIO_COEF_ONE - 1;
63    }
64    return (audio_sample_t) (acc >> AUDIO_COEF_PRECISION);
65}
66
67// Convert a S15 sample to audio_sample_t
68inline audio_sample_t s15_to_audio_sample_t(int16_t s15) {
69    return audio_sample_t(s15) << 9;
70}
71
72// Convert a audio_sample_t sample to S15 (no clipping)
73inline int16_t audio_sample_t_to_s15(audio_sample_t sample) {
74    return int16_t((sample + (1 << 8)) >> 9);
75}
76
77// Convert a audio_sample_t sample to S15 (with clipping)
78inline int16_t audio_sample_t_to_s15_clip(audio_sample_t sample) {
79    // TODO: optimize for targets supporting this as an atomic operation.
80    if (CC_UNLIKELY(sample >= (0x7FFF << 9))) {
81        return 0x7FFF;
82    } else if (CC_UNLIKELY(sample <= -(0x8000 << 9))) {
83        return 0x8000;
84    } else {
85        return audio_sample_t_to_s15(sample);
86    }
87}
88
89////////////////////////////////////////////////////////////////////////////////
90
91}
92
93#endif // ANDROID_AUDIO_COMMON_H
94