1 /*
2 * Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "common_audio/smoothing_filter.h"
12
13 #include <cmath>
14 #include <memory>
15
16 #include "rtc_base/fake_clock.h"
17 #include "test/gtest.h"
18
19 namespace webrtc {
20
21 namespace {
22
23 constexpr float kMaxAbsError = 1e-5f;
24 constexpr int64_t kClockInitialTime = 123456;
25
26 struct SmoothingFilterStates {
SmoothingFilterStateswebrtc::__anonfa266f5e0111::SmoothingFilterStates27 explicit SmoothingFilterStates(int init_time_ms)
28 : smoothing_filter(init_time_ms) {
29 fake_clock.AdvanceTime(TimeDelta::Millis(kClockInitialTime));
30 }
31 rtc::ScopedFakeClock fake_clock;
32 SmoothingFilterImpl smoothing_filter;
33 };
34
35 // This function does the following:
36 // 1. Add a sample to filter at current clock,
37 // 2. Advance the clock by |advance_time_ms|,
38 // 3. Get the output of both SmoothingFilter and verify that it equals to an
39 // expected value.
CheckOutput(SmoothingFilterStates * states,float sample,int advance_time_ms,float expected_ouput)40 void CheckOutput(SmoothingFilterStates* states,
41 float sample,
42 int advance_time_ms,
43 float expected_ouput) {
44 states->smoothing_filter.AddSample(sample);
45 states->fake_clock.AdvanceTime(TimeDelta::Millis(advance_time_ms));
46 auto output = states->smoothing_filter.GetAverage();
47 EXPECT_TRUE(output);
48 EXPECT_NEAR(expected_ouput, *output, kMaxAbsError);
49 }
50
51 } // namespace
52
TEST(SmoothingFilterTest,NoOutputWhenNoSampleAdded)53 TEST(SmoothingFilterTest, NoOutputWhenNoSampleAdded) {
54 constexpr int kInitTimeMs = 100;
55 SmoothingFilterStates states(kInitTimeMs);
56 EXPECT_FALSE(states.smoothing_filter.GetAverage());
57 }
58
59 // Python script to calculate the reference values used in this test.
60 // import math
61 //
62 // class ExpFilter:
63 // def add_sample(self, new_value):
64 // self.state = self.state * self.alpha + (1.0 - self.alpha) * new_value
65 //
66 // filter = ExpFilter()
67 // init_time = 795
68 // init_factor = (1.0 / init_time) ** (1.0 / init_time)
69 //
70 // filter.state = 1.0
71 //
72 // for time_now in range(1, 500):
73 // filter.alpha = math.exp(-init_factor ** time_now)
74 // filter.add_sample(1.0)
75 // print filter.state
76 //
77 // for time_now in range(500, 600):
78 // filter.alpha = math.exp(-init_factor ** time_now)
79 // filter.add_sample(0.5)
80 // print filter.state
81 //
82 // for time_now in range(600, 700):
83 // filter.alpha = math.exp(-init_factor ** time_now)
84 // filter.add_sample(1.0)
85 // print filter.state
86 //
87 // for time_now in range(700, init_time):
88 // filter.alpha = math.exp(-init_factor ** time_now)
89 // filter.add_sample(1.0)
90 //
91 // filter.alpha = math.exp(-1.0 / init_time)
92 // for time_now in range(init_time, 800):
93 // filter.add_sample(1.0)
94 // print filter.state
95 //
96 // for i in range(800, 900):
97 // filter.add_sample(0.5)
98 // print filter.state
99 //
100 // for i in range(900, 1000):
101 // filter.add_sample(1.0)
102 // print filter.state
TEST(SmoothingFilterTest,CheckBehaviorAroundInitTime)103 TEST(SmoothingFilterTest, CheckBehaviorAroundInitTime) {
104 constexpr int kInitTimeMs = 795;
105 SmoothingFilterStates states(kInitTimeMs);
106 CheckOutput(&states, 1.0f, 500, 1.0f);
107 CheckOutput(&states, 0.5f, 100, 0.680562264029f);
108 CheckOutput(&states, 1.0f, 100, 0.794207139813f);
109 // Next step will go across initialization time.
110 CheckOutput(&states, 1.0f, 100, 0.829803409752f);
111 CheckOutput(&states, 0.5f, 100, 0.790821764210f);
112 CheckOutput(&states, 1.0f, 100, 0.815545922911f);
113 }
114
TEST(SmoothingFilterTest,InitTimeEqualsZero)115 TEST(SmoothingFilterTest, InitTimeEqualsZero) {
116 constexpr int kInitTimeMs = 0;
117 SmoothingFilterStates states(kInitTimeMs);
118 CheckOutput(&states, 1.0f, 1, 1.0f);
119 CheckOutput(&states, 0.5f, 1, 0.5f);
120 }
121
TEST(SmoothingFilterTest,InitTimeEqualsOne)122 TEST(SmoothingFilterTest, InitTimeEqualsOne) {
123 constexpr int kInitTimeMs = 1;
124 SmoothingFilterStates states(kInitTimeMs);
125 CheckOutput(&states, 1.0f, 1, 1.0f);
126 CheckOutput(&states, 0.5f, 1,
127 1.0f * std::exp(-1.0f) + (1.0f - std::exp(-1.0f)) * 0.5f);
128 }
129
TEST(SmoothingFilterTest,GetAverageOutputsEmptyBeforeFirstSample)130 TEST(SmoothingFilterTest, GetAverageOutputsEmptyBeforeFirstSample) {
131 constexpr int kInitTimeMs = 100;
132 SmoothingFilterStates states(kInitTimeMs);
133 EXPECT_FALSE(states.smoothing_filter.GetAverage());
134 constexpr float kFirstSample = 1.2345f;
135 states.smoothing_filter.AddSample(kFirstSample);
136 EXPECT_EQ(kFirstSample, states.smoothing_filter.GetAverage());
137 }
138
TEST(SmoothingFilterTest,CannotChangeTimeConstantDuringInitialization)139 TEST(SmoothingFilterTest, CannotChangeTimeConstantDuringInitialization) {
140 constexpr int kInitTimeMs = 100;
141 SmoothingFilterStates states(kInitTimeMs);
142 states.smoothing_filter.AddSample(0.0);
143
144 // During initialization, |SetTimeConstantMs| does not take effect.
145 states.fake_clock.AdvanceTime(TimeDelta::Millis(kInitTimeMs - 1));
146 states.smoothing_filter.AddSample(0.0);
147
148 EXPECT_FALSE(states.smoothing_filter.SetTimeConstantMs(kInitTimeMs * 2));
149 EXPECT_NE(std::exp(-1.0f / (kInitTimeMs * 2)),
150 states.smoothing_filter.alpha());
151
152 states.fake_clock.AdvanceTime(TimeDelta::Millis(1));
153 states.smoothing_filter.AddSample(0.0);
154 // When initialization finishes, the time constant should be come
155 // |kInitTimeConstantMs|.
156 EXPECT_FLOAT_EQ(std::exp(-1.0f / kInitTimeMs),
157 states.smoothing_filter.alpha());
158
159 // After initialization, |SetTimeConstantMs| takes effect.
160 EXPECT_TRUE(states.smoothing_filter.SetTimeConstantMs(kInitTimeMs * 2));
161 EXPECT_FLOAT_EQ(std::exp(-1.0f / (kInitTimeMs * 2)),
162 states.smoothing_filter.alpha());
163 }
164
165 } // namespace webrtc
166