Adding SmoothingFilter to audio network adaptor.

webrtc/modules/audio_coding/audio_network_adaptor/smoothing_filter_unittest.cc

+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <memory>
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/modules/audio_coding/audio_network_adaptor/smoothing_filter.h"
+
+namespace webrtc {
+
+namespace {
+
+constexpr int kTimeConstantMs = 1000;
+constexpr float kMaxAbsError = 0.0001f;
+constexpr int64_t kClockInitialTime = 123456;
+
+struct SmoothingFilterStates {
+  std::unique_ptr<SimulatedClock> simulated_clock;
+  std::unique_ptr<SmoothingFilter> smoothing_filter;
+};
+
+SmoothingFilterStates CreateSmoothingFilter() {
+  SmoothingFilterStates states;
+  states.simulated_clock.reset(new SimulatedClock(kClockInitialTime));
+  states.smoothing_filter.reset(
+      new SmoothingFilterImpl(kTimeConstantMs, states.simulated_clock.get()));
+  return states;
+}
+
+void CheckOutput(SmoothingFilterStates* states,
+                 int advance_time_ms,
+                 float sample,
+                 float expected_ouput) {
+  states->simulated_clock->AdvanceTimeMilliseconds(advance_time_ms);
+  states->smoothing_filter->AddSample(sample);
+  auto output = states->smoothing_filter->GetAverage();
+  EXPECT_TRUE(output);
+  EXPECT_NEAR(expected_ouput, *output, kMaxAbsError);
+}
+
+}  // namespace
+
+TEST(SmoothingFilterTest, NoOutputWhenNoSampleAdded) {
+  auto states = CreateSmoothingFilter();
+  EXPECT_FALSE(states.smoothing_filter->GetAverage());
+}
+
+// Python script to calculate the reference values used in this test.
+//  import math
+//
+//  class ExpFilter:
+//    alpha = 0.0
+//    old_value = 0.0
+//    def calc(self, new_value):
+//      self.old_value = self.old_value * self.alpha
+//                       + (1.0 - self.alpha) * new_value
+//      return self.old_value
+//
+//  delta_t = 100.0
+//  filter = ExpFilter()
+//  total_t = 100.0
+//  filter.alpha = math.exp(-delta_t/ total_t)
+//  print filter.calc(1.0)
+//  total_t = 200.0
+//  filter.alpha = math.exp(-delta_t/ total_t)
+//  print filter.calc(0.0)
+//  total_t = 300.0
+//  filter.alpha = math.exp(-delta_t/ total_t)
+//  print filter.calc(1.0)
+TEST(SmoothingFilterTest, CheckBehaviorBeforeInitialized) {
+  // Adding three samples, all added before |kTimeConstantMs| is reached.
+  constexpr int kTimeIntervalMs = 100;
+  auto states = CreateSmoothingFilter();
+  states.smoothing_filter->AddSample(0.0);
+  CheckOutput(&states, kTimeIntervalMs, 1.0, 0.63212f);
+  CheckOutput(&states, kTimeIntervalMs, 0.0, 0.38340f);
+  CheckOutput(&states, kTimeIntervalMs, 1.0, 0.55818f);
+}
+
+// Python script to calculate the reference value used in this test.
+// (after defining ExpFilter as for CheckBehaviorBeforeInitialized)
+//  time_constant_ms = 1000.0
+//  filter = ExpFilter()
+//  delta_t = 1100.0
+//  filter.alpha = math.exp(-delta_t/ time_constant_ms)
+//  print filter.calc(1.0)
+//  delta_t = 100.0
+//  filter.alpha = math.exp(-delta_t/ time_constant_ms)
+//  print filter.calc(0.0)
+//  print filter.calc(1.0)
+TEST(SmoothingFilterTest, CheckBehaviorAfterInitialized) {
+  constexpr int kTimeIntervalMs = 100;
+  auto states = CreateSmoothingFilter();
+  states.smoothing_filter->AddSample(0.0);
+  states.simulated_clock->AdvanceTimeMilliseconds(kTimeConstantMs);
+  CheckOutput(&states, kTimeIntervalMs, 1.0, 0.66713f);
+  CheckOutput(&states, kTimeIntervalMs, 0.0, 0.60364f);
+  CheckOutput(&states, kTimeIntervalMs, 1.0, 0.64136f);
+}
+
+}  // namespace webrtc