[Chromoting] Add AudioVolumeApplier to reduce the complexity and the dependency of kChannels

remoting/host/audio_volume_applier_unittest.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/audio_volume_applier.h"
+
+#include "base/macros.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace remoting {
+
+namespace {
+
+class FakeAudioVolumeApplier : public AudioVolumeApplier {
+ public:
+  FakeAudioVolumeApplier(int silence_threshold)
+      : AudioVolumeApplier(silence_threshold) {}
+  ~FakeAudioVolumeApplier() override = default;
+
+  void set_audio_level(float level) { level_ = level; }
+
+ protected:
+  float GetAudioLevel() override { return level_; }
+
+ private:
+  float level_ = 0;
+};
+
+}  // namespace
+
+TEST(AudioVolumeApplierTest, TwoChannels) {
+  int16_t samples[] =
+      {1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10};
+  FakeAudioVolumeApplier applier(0);
+  applier.set_audio_level(0.5f);
+  applier.Initialize(9, 2);
+  // After applying the audio volume, the |samples| should still pass the
+  // AudioSilenceDetector, AudioVolumeApplier::Apply() returns true under this
+  // condition. Ditto.
+  ASSERT_TRUE(applier.Apply(samples, arraysize(samples) / 2));
+}
+
+TEST(AudioVolumeApplierTest, ThreeChannels) {
+  int16_t samples[] =
+      {1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11};
+  FakeAudioVolumeApplier applier(0);
+  applier.set_audio_level(0.5f);
+  applier.Initialize(6, 3);
+  ASSERT_TRUE(applier.Apply(samples, arraysize(samples) / 3));
+}
+
+TEST(AudioVolumeApplierTest, SilentSamples) {
+  int16_t samples[] =
+      {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+  FakeAudioVolumeApplier applier(0);
+  applier.set_audio_level(0.5f);
+  applier.Initialize(9, 2);
+  ASSERT_FALSE(applier.Apply(samples, arraysize(samples) / 2));
+}
+
+TEST(AudioVolumeApplierTest, AudioLevel0) {
+  int16_t samples[] =
+      {1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10};
+  FakeAudioVolumeApplier applier(0);
+  applier.set_audio_level(0);
+  applier.Initialize(9, 2);
+  ASSERT_FALSE(applier.Apply(samples, arraysize(samples) / 2));
+}
+
+TEST(AudioVolumeApplierTest, SilcentAfterApplying) {
+  int16_t samples[] =
+      {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
+  FakeAudioVolumeApplier applier(0);
+  applier.set_audio_level(0.9f);
+  applier.Initialize(9, 2);
+  ASSERT_FALSE(applier.Apply(samples, arraysize(samples) / 2));
+}
+
+}  // namespace remoting