1 /*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <cmath>
18
19 #include "common/core/math.h"
20 #include "common/core/types.h"
21 #include "dsp/core/basic.h"
22 #include "dsp/core/interpolation.h"
23 #include "dsp/core/dynamic_range_compression.h"
24
25 //#define LOG_NDEBUG 0
26 #include <cutils/log.h>
27
28
29 namespace le_fx {
30
31 // Definitions for static const class members declared in
32 // dynamic_range_compression.h.
33 const float AdaptiveDynamicRangeCompression::kMinAbsValue = 0.000001f;
34 const float AdaptiveDynamicRangeCompression::kMinLogAbsValue =
35 0.032766999999999997517097227728299912996590137481689453125f;
36 const float AdaptiveDynamicRangeCompression::kFixedPointLimit = 32767.0f;
37 const float AdaptiveDynamicRangeCompression::kInverseFixedPointLimit =
38 1.0f / AdaptiveDynamicRangeCompression::kFixedPointLimit;
39 const float AdaptiveDynamicRangeCompression::kDefaultKneeThresholdInDecibel =
40 -8.0f;
41 const float AdaptiveDynamicRangeCompression::kCompressionRatio = 7.0f;
42 const float AdaptiveDynamicRangeCompression::kTauAttack = 0.001f;
43 const float AdaptiveDynamicRangeCompression::kTauRelease = 0.015f;
44
AdaptiveDynamicRangeCompression()45 AdaptiveDynamicRangeCompression::AdaptiveDynamicRangeCompression() {
46 static const float kTargetGain[] = {
47 1.0f, 2.0f, 3.0f, 4.0f, 5.0f };
48 static const float kKneeThreshold[] = {
49 -8.0f, -8.0f, -8.5f, -9.0f, -10.0f };
50 target_gain_to_knee_threshold_.Initialize(
51 &kTargetGain[0], &kKneeThreshold[0],
52 sizeof(kTargetGain) / sizeof(kTargetGain[0]));
53 }
54
Initialize(float target_gain,float sampling_rate)55 bool AdaptiveDynamicRangeCompression::Initialize(
56 float target_gain, float sampling_rate) {
57 set_knee_threshold_via_target_gain(target_gain);
58 sampling_rate_ = sampling_rate;
59 state_ = 0.0f;
60 compressor_gain_ = 1.0f;
61 if (kTauAttack > 0.0f) {
62 const float taufs = kTauAttack * sampling_rate_;
63 alpha_attack_ = std::exp(-1.0f / taufs);
64 } else {
65 alpha_attack_ = 0.0f;
66 }
67 if (kTauRelease > 0.0f) {
68 const float taufs = kTauRelease * sampling_rate_;
69 alpha_release_ = std::exp(-1.0f / taufs);
70 } else {
71 alpha_release_ = 0.0f;
72 }
73 // Feed-forward topology
74 slope_ = 1.0f / kCompressionRatio - 1.0f;
75 return true;
76 }
77
Compress(float x)78 float AdaptiveDynamicRangeCompression::Compress(float x) {
79 const float max_abs_x = std::max(std::fabs(x), kMinLogAbsValue);
80 const float max_abs_x_dB = math::fast_log(max_abs_x);
81 // Subtract Threshold from log-encoded input to get the amount of overshoot
82 const float overshoot = max_abs_x_dB - knee_threshold_;
83 // Hard half-wave rectifier
84 const float rect = std::max(overshoot, 0.0f);
85 // Multiply rectified overshoot with slope
86 const float cv = rect * slope_;
87 const float prev_state = state_;
88 if (cv <= state_) {
89 state_ = alpha_attack_ * state_ + (1.0f - alpha_attack_) * cv;
90 } else {
91 state_ = alpha_release_ * state_ + (1.0f - alpha_release_) * cv;
92 }
93 compressor_gain_ *=
94 math::ExpApproximationViaTaylorExpansionOrder5(state_ - prev_state);
95 x *= compressor_gain_;
96 if (x > kFixedPointLimit) {
97 return kFixedPointLimit;
98 }
99 if (x < -kFixedPointLimit) {
100 return -kFixedPointLimit;
101 }
102 return x;
103 }
104
Compress(float * x1,float * x2)105 void AdaptiveDynamicRangeCompression::Compress(float *x1, float *x2) {
106 // Taking the maximum amplitude of both channels
107 const float max_abs_x = std::max(std::fabs(*x1),
108 std::max(std::fabs(*x2), kMinLogAbsValue));
109 const float max_abs_x_dB = math::fast_log(max_abs_x);
110 // Subtract Threshold from log-encoded input to get the amount of overshoot
111 const float overshoot = max_abs_x_dB - knee_threshold_;
112 // Hard half-wave rectifier
113 const float rect = std::max(overshoot, 0.0f);
114 // Multiply rectified overshoot with slope
115 const float cv = rect * slope_;
116 const float prev_state = state_;
117 if (cv <= state_) {
118 state_ = alpha_attack_ * state_ + (1.0f - alpha_attack_) * cv;
119 } else {
120 state_ = alpha_release_ * state_ + (1.0f - alpha_release_) * cv;
121 }
122 compressor_gain_ *=
123 math::ExpApproximationViaTaylorExpansionOrder5(state_ - prev_state);
124 *x1 *= compressor_gain_;
125 if (*x1 > kFixedPointLimit) {
126 *x1 = kFixedPointLimit;
127 }
128 if (*x1 < -kFixedPointLimit) {
129 *x1 = -kFixedPointLimit;
130 }
131 *x2 *= compressor_gain_;
132 if (*x2 > kFixedPointLimit) {
133 *x2 = kFixedPointLimit;
134 }
135 if (*x2 < -kFixedPointLimit) {
136 *x2 = -kFixedPointLimit;
137 }
138 }
139
140 } // namespace le_fx
141
142