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 
25 namespace android {
26 
27 // Audio coefficient type.
28 typedef int32_t audio_coef_t;
29 // Audio sample type.
30 typedef int32_t audio_sample_t;
31 // Accumulator type for coef x sample.
32 typedef int64_t audio_coef_sample_acc_t;
33 
34 // Number of fraction bits for audio coefficient.
35 static const int AUDIO_COEF_PRECISION = 24;
36 // Audio coefficient with the value of 1.0
37 static const audio_coef_t AUDIO_COEF_ONE = 1 << AUDIO_COEF_PRECISION;
38 // Audio coefficient with the value of 0.5
39 static const audio_coef_t AUDIO_COEF_HALF = 1 << (AUDIO_COEF_PRECISION - 1);
40 // Number of fraction bits for audio sample.
41 static const int AUDIO_SAMPLE_PRECISION = 24;
42 // Audio sample with the value of 1.0
43 static 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.
mul_coef_sample(audio_coef_t x,audio_sample_t y)50 inline 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.
mac_coef_sample(audio_coef_t x,audio_sample_t y,audio_coef_sample_acc_t acc)55 inline 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.
coef_sample_acc_to_sample(audio_coef_sample_acc_t acc)60 inline 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
s15_to_audio_sample_t(int16_t s15)68 inline 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)
audio_sample_t_to_s15(audio_sample_t sample)73 inline 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)
audio_sample_t_to_s15_clip(audio_sample_t sample)78 inline 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