Changed mixing to be done at the minimal possible frequency.

webrtc/modules/audio_mixer/audio_mixer_impl_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.
  */
 
@@ skipping 38 matching lines @@
 
 }  // namespace
 
 class MockMixerAudioSource : public AudioMixer::Source {
  public:
   MockMixerAudioSource()
       : fake_audio_frame_info_(AudioMixer::Source::AudioFrameInfo::kNormal) {
     ON_CALL(*this, GetAudioFrameWithInfo(_, _))
         .WillByDefault(
             Invoke(this, &MockMixerAudioSource::FakeAudioFrameWithInfo));
+    ON_CALL(*this, PreferredSampleRate())
+        .WillByDefault(Return(kDefaultSampleRateHz));
   }
 
   MOCK_METHOD2(GetAudioFrameWithInfo,
                AudioFrameInfo(int sample_rate_hz, AudioFrame* audio_frame));
 
   MOCK_CONST_METHOD0(PreferredSampleRate, int());
   MOCK_CONST_METHOD0(Ssrc, int());
 
   AudioFrame* fake_frame() { return &fake_frame_; }
   AudioFrameInfo fake_info() { return fake_audio_frame_info_; }
@@ skipping 28 matching lines @@
     participants[i].fake_frame()->CopyFrom(frames[i]);
     participants[i].set_fake_info(frame_info[i]);
   }
 
   for (int i = 0; i < num_audio_sources; i++) {
     EXPECT_TRUE(mixer->AddSource(&participants[i]));
     EXPECT_CALL(participants[i], GetAudioFrameWithInfo(kDefaultSampleRateHz, _))
         .Times(Exactly(1));
   }
 
-  mixer->Mix(kDefaultSampleRateHz, 1, &frame_for_mixing);
+  mixer->Mix(1, &frame_for_mixing);
 
   for (int i = 0; i < num_audio_sources; i++) {
     EXPECT_EQ(expected_status[i],
               mixer->GetAudioSourceMixabilityStatusForTest(&participants[i]))
         << "Mixed status of AudioSource #" << i << " wrong.";
   }
 }
 
+void MixMonoAtGivenNativeRate(int native_sample_rate,
+                              AudioFrame* mix_frame,
+                              rtc::scoped_refptr<AudioMixer> mixer,
+                              MockMixerAudioSource* audio_source) {
+  ON_CALL(*audio_source, PreferredSampleRate())
+      .WillByDefault(Return(native_sample_rate));
+  audio_source->fake_frame()->sample_rate_hz_ = native_sample_rate;
+  audio_source->fake_frame()->samples_per_channel_ = native_sample_rate / 100;
+
+  mixer->Mix(1, mix_frame);
+}
+
 TEST(AudioMixer, LargestEnergyVadActiveMixed) {
   constexpr int kAudioSources =
       AudioMixerImpl::kMaximumAmountOfMixedAudioSources + 3;
 
   const auto mixer = AudioMixerImpl::Create();
 
   MockMixerAudioSource participants[kAudioSources];
 
   for (int i = 0; i < kAudioSources; ++i) {
     ResetFrame(participants[i].fake_frame());
 
     // We set the 80-th sample value since the first 80 samples may be
     // modified by a ramped-in window.
     participants[i].fake_frame()->data_[80] = i;
 
     EXPECT_TRUE(mixer->AddSource(&participants[i]));
     EXPECT_CALL(participants[i], GetAudioFrameWithInfo(_, _)).Times(Exactly(1));
   }
 
   // Last participant gives audio frame with passive VAD, although it has the
   // largest energy.
   participants[kAudioSources - 1].fake_frame()->vad_activity_ =
       AudioFrame::kVadPassive;
 
   AudioFrame audio_frame;
-  mixer->Mix(kDefaultSampleRateHz,
-             1,  // number of channels
+  mixer->Mix(1,  // number of channels
              &audio_frame);
 
   for (int i = 0; i < kAudioSources; ++i) {
     bool is_mixed =
         mixer->GetAudioSourceMixabilityStatusForTest(&participants[i]);
     if (i == kAudioSources - 1 ||
         i < kAudioSources - 1 -
                 AudioMixerImpl::kMaximumAmountOfMixedAudioSources) {
       EXPECT_FALSE(is_mixed) << "Mixing status of AudioSource #" << i
                              << " wrong.";
@@ skipping 16 matching lines @@
   for (int j = 0; j < n_samples; j++) {
     participant.fake_frame()->data_[j] = j;
   }
 
   EXPECT_TRUE(mixer->AddSource(&participant));
   EXPECT_CALL(participant, GetAudioFrameWithInfo(_, _)).Times(Exactly(2));
 
   AudioFrame audio_frame;
   // Two mix iteration to compare after the ramp-up step.
   for (int i = 0; i < 2; i++) {
-    mixer->Mix(kDefaultSampleRateHz,
-               1,  // number of channels
+    mixer->Mix(1,  // number of channels
                &audio_frame);
   }
 
   EXPECT_EQ(
       0, memcmp(participant.fake_frame()->data_, audio_frame.data_, n_samples));
 }
 

[aleloi, 2016/10/31 10:39:35]

The rationale behind the change of ParticipantSampleRate is as follows.

Test 3 behaviors:

* That there should be no resampling when all sources run on the same native
rate (tested by checking that the sample rate argument of GetAudioWithInfo is
the source's requested rate)

* That the mixed result is at the same rate if all sources have the same native
rate (tested by inspecting the mixed rate).

* That non-native source rates are converted by the mixer to larger native
rates.

-TEST(AudioMixer, ParticipantSampleRate) {
+TEST(AudioMixer, SourceAtNativeRateShouldNeverResample) {
+  const auto mixer = AudioMixerImpl::Create();
+
+  MockMixerAudioSource audio_source;
+  ResetFrame(audio_source.fake_frame());
+
+  mixer->AddSource(&audio_source);
+
+  for (auto frequency : {8000, 16000, 32000, 48000}) {
+    EXPECT_CALL(audio_source, GetAudioFrameWithInfo(frequency, _))
+        .Times(Exactly(1));
+
+    MixMonoAtGivenNativeRate(frequency, &frame_for_mixing, mixer,
+                             &audio_source);
+  }
+}
+
+TEST(AudioMixer, MixerShouldMixAtNativeSourceRate) {
+  const auto mixer = AudioMixerImpl::Create();
+
+  MockMixerAudioSource audio_source;
+  ResetFrame(audio_source.fake_frame());
+
+  mixer->AddSource(&audio_source);
+
+  for (auto frequency : {8000, 16000, 32000, 48000}) {
+    MixMonoAtGivenNativeRate(frequency, &frame_for_mixing, mixer,
+                             &audio_source);
+
+    EXPECT_EQ(frequency, frame_for_mixing.sample_rate_hz_);
+  }
+}
+
+TEST(AudioMixer, MixerShouldAlwaysMixAtNativeRate) {
   const auto mixer = AudioMixerImpl::Create();
 
   MockMixerAudioSource participant;
   ResetFrame(participant.fake_frame());
+  mixer->AddSource(&participant);
 
-  EXPECT_TRUE(mixer->AddSource(&participant));
-  for (auto frequency : {8000, 16000, 32000, 48000}) {
-    EXPECT_CALL(participant, GetAudioFrameWithInfo(frequency, _))
-        .Times(Exactly(1));
-    participant.fake_frame()->sample_rate_hz_ = frequency;
-    participant.fake_frame()->samples_per_channel_ = frequency / 100;
-    mixer->Mix(frequency, 1, &frame_for_mixing);
-    EXPECT_EQ(frequency, frame_for_mixing.sample_rate_hz_);
-  }
+  const int needed_frequency = 44100;
+  ON_CALL(participant, PreferredSampleRate())
+      .WillByDefault(Return(needed_frequency));
+
+  // We expect mixing frequency to be native and >= needed_frequency.
+  const int expected_mix_frequency = 48000;
+  EXPECT_CALL(participant, GetAudioFrameWithInfo(expected_mix_frequency, _))
+      .Times(Exactly(1));
+  participant.fake_frame()->sample_rate_hz_ = expected_mix_frequency;
+  participant.fake_frame()->samples_per_channel_ = expected_mix_frequency / 100;
+
+  mixer->Mix(1, &frame_for_mixing);
+
+  EXPECT_EQ(48000, frame_for_mixing.sample_rate_hz_);
 }
 
 TEST(AudioMixer, ParticipantNumberOfChannels) {
   const auto mixer = AudioMixerImpl::Create();
 
   MockMixerAudioSource participant;
   ResetFrame(participant.fake_frame());
 
   EXPECT_TRUE(mixer->AddSource(&participant));
   for (size_t number_of_channels : {1, 2}) {
     EXPECT_CALL(participant, GetAudioFrameWithInfo(kDefaultSampleRateHz, _))
         .Times(Exactly(1));
-    mixer->Mix(kDefaultSampleRateHz, number_of_channels, &frame_for_mixing);
+    mixer->Mix(number_of_channels, &frame_for_mixing);
     EXPECT_EQ(number_of_channels, frame_for_mixing.num_channels_);
   }
 }
 
 // Maximal amount of participants are mixed one iteration, then
 // another participant with higher energy is added.
 TEST(AudioMixer, RampedOutSourcesShouldNotBeMarkedMixed) {
   constexpr int kAudioSources =
       AudioMixerImpl::kMaximumAmountOfMixedAudioSources + 1;
 
   const auto mixer = AudioMixerImpl::Create();
   MockMixerAudioSource participants[kAudioSources];
 
   for (int i = 0; i < kAudioSources; i++) {
     ResetFrame(participants[i].fake_frame());
     // Set the participant audio energy to increase with the index
     // |i|.
     participants[i].fake_frame()->data_[0] = 100 * i;
   }
 
   // Add all participants but the loudest for mixing.
   for (int i = 0; i < kAudioSources - 1; i++) {
     EXPECT_TRUE(mixer->AddSource(&participants[i]));
     EXPECT_CALL(participants[i], GetAudioFrameWithInfo(kDefaultSampleRateHz, _))
         .Times(Exactly(1));
   }
 
   // First mixer iteration
-  mixer->Mix(kDefaultSampleRateHz, 1, &frame_for_mixing);
+  mixer->Mix(1, &frame_for_mixing);
 
   // All participants but the loudest should have been mixed.
   for (int i = 0; i < kAudioSources - 1; i++) {
     EXPECT_TRUE(mixer->GetAudioSourceMixabilityStatusForTest(&participants[i]))
         << "Mixed status of AudioSource #" << i << " wrong.";
   }
 
   // Add new participant with higher energy.
   EXPECT_TRUE(mixer->AddSource(&participants[kAudioSources - 1]));
   for (int i = 0; i < kAudioSources; i++) {
     EXPECT_CALL(participants[i], GetAudioFrameWithInfo(kDefaultSampleRateHz, _))
         .Times(Exactly(1));
   }
 
-  mixer->Mix(kDefaultSampleRateHz, 1, &frame_for_mixing);
+  mixer->Mix(1, &frame_for_mixing);
 
   // The most quiet participant should not have been mixed.
   EXPECT_FALSE(mixer->GetAudioSourceMixabilityStatusForTest(&participants[0]))
       << "Mixed status of AudioSource #0 wrong.";
 
   // The loudest participants should have been mixed.
   for (int i = 1; i < kAudioSources; i++) {
     EXPECT_EQ(true,
               mixer->GetAudioSourceMixabilityStatusForTest(&participants[i]))
         << "Mixed status of AudioSource #" << i << " wrong.";
@@ skipping 14 matching lines @@
 
   participant_thread->Start();
   EXPECT_TRUE(participant_thread->Invoke<int>(
       RTC_FROM_HERE,
       rtc::Bind(&AudioMixer::AddSource, mixer.get(), &participant)));
 
   EXPECT_CALL(participant, GetAudioFrameWithInfo(kDefaultSampleRateHz, _))
       .Times(Exactly(1));
 
   // Do one mixer iteration
-  mixer->Mix(kDefaultSampleRateHz, 1, &frame_for_mixing);
+  mixer->Mix(1, &frame_for_mixing);
 }
 
 TEST(AudioMixer, MutedShouldMixAfterUnmuted) {
   constexpr int kAudioSources =
       AudioMixerImpl::kMaximumAmountOfMixedAudioSources + 1;
 
   std::vector<AudioFrame> frames(kAudioSources);
   for (auto& frame : frames) {
     ResetFrame(&frame);
   }
@@ skipping 58 matching lines @@
       kAudioSources, AudioMixer::Source::AudioFrameInfo::kNormal);
   frame_info[0] = AudioMixer::Source::AudioFrameInfo::kMuted;
   std::fill(frames[0].data_, frames[0].data_ + kDefaultSampleRateHz / 100,
             std::numeric_limits<int16_t>::max());
   std::vector<bool> expected_status(kAudioSources, true);
   expected_status[0] = false;
 
   MixAndCompare(frames, frame_info, expected_status);
 }
 }  // namespace webrtc