audio/audio_manager_unittest.cc

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/audio/audio_manager.h"

#include <map>
#include <memory>
#include <utility>
#include <vector>

#include "base/command_line.h"
#include "base/environment.h"
#include "base/functional/bind.h"
#include "base/logging.h"
#include "base/memory/raw_ptr.h"
#include "base/ranges/algorithm.h"
#include "base/run_loop.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "base/synchronization/waitable_event.h"
#include "base/system/sys_info.h"
#include "base/task/single_thread_task_runner.h"
#include "base/test/test_message_loop.h"
#include "build/build_config.h"
#include "build/chromeos_buildflags.h"
#include "media/audio/audio_device_description.h"
#include "media/audio/audio_device_info_accessor_for_tests.h"
#include "media/audio/audio_device_name.h"
#include "media/audio/audio_output_proxy.h"
#include "media/audio/audio_unittest_util.h"
#include "media/audio/fake_audio_log_factory.h"
#include "media/audio/fake_audio_manager.h"
#include "media/audio/test_audio_thread.h"
#include "media/base/limits.h"
#include "media/base/media_switches.h"
#include "testing/gmock/include/gmock/gmock.h"
#include "testing/gtest/include/gtest/gtest.h"

#if defined(USE_ALSA)
#include "media/audio/alsa/audio_manager_alsa.h"
#endif  // defined(USE_ALSA)

#if BUILDFLAG(IS_MAC)
#include "media/audio/mac/audio_manager_mac.h"
#include "media/base/mac/audio_latency_mac.h"
#endif

#if BUILDFLAG(IS_WIN)
#include "base/win/scoped_com_initializer.h"
#include "media/audio/win/audio_manager_win.h"
#endif

#if defined(USE_PULSEAUDIO)
#include "media/audio/pulse/audio_manager_pulse.h"
#include "media/audio/pulse/pulse_util.h"
#endif  // defined(USE_PULSEAUDIO)

#if defined(USE_CRAS)
#include "media/audio/cras/audio_manager_cras.h"
#endif

namespace media {
namespace {

template <typename T>
struct TestAudioManagerFactory {
  static std::unique_ptr<AudioManager> Create(
      AudioLogFactory* audio_log_factory) {
    return std::make_unique<T>(std::make_unique<TestAudioThread>(),
                               audio_log_factory);
  }
};

#if defined(USE_PULSEAUDIO)
template <>
struct TestAudioManagerFactory<AudioManagerPulse> {
  static std::unique_ptr<AudioManager> Create(
      AudioLogFactory* audio_log_factory) {
    pa_threaded_mainloop* pa_mainloop = nullptr;
    pa_context* pa_context = nullptr;
    if (!pulse::InitPulse(&pa_mainloop, &pa_context))
      return nullptr;
    return std::make_unique<AudioManagerPulse>(
        std::make_unique<TestAudioThread>(), audio_log_factory, pa_mainloop,
        pa_context);
  }
};
#endif  // defined(USE_PULSEAUDIO)

template <>
struct TestAudioManagerFactory<std::nullptr_t> {
  static std::unique_ptr<AudioManager> Create(
      AudioLogFactory* audio_log_factory) {
    return AudioManager::CreateForTesting(std::make_unique<TestAudioThread>());
  }
};

const char kRealDefaultInputDeviceID[] = "input2";
const char kRealDefaultOutputDeviceID[] = "output3";
const char kRealCommunicationsInputDeviceID[] = "input1";
const char kRealCommunicationsOutputDeviceID[] = "output1";

void CheckDescriptionLabels(const AudioDeviceDescriptions& descriptions,
                            const std::string& real_default_id,
                            const std::string& real_communications_id) {
  std::string real_default_label;
  std::string real_communications_label;
  for (const auto& description : descriptions) {
    if (description.unique_id == real_default_id)
      real_default_label = description.device_name;
    else if (description.unique_id == real_communications_id)
      real_communications_label = description.device_name;
  }

  for (const auto& description : descriptions) {
    if (AudioDeviceDescription::IsDefaultDevice(description.unique_id)) {
      EXPECT_TRUE(base::EndsWith(description.device_name, real_default_label,
                                 base::CompareCase::SENSITIVE));
    } else if (description.unique_id ==
               AudioDeviceDescription::kCommunicationsDeviceId) {
      EXPECT_TRUE(base::EndsWith(description.device_name,
                                 real_communications_label,
                                 base::CompareCase::SENSITIVE));
    } else if (description.unique_id == real_default_id) {
      EXPECT_TRUE(description.is_system_default);
    }
  }
}

}  // namespace

// Test fixture which allows us to override the default enumeration API on
// Windows.
class AudioManagerTest : public ::testing::Test {
 public:
  void HandleDefaultDeviceIDsTest() {
    AudioParameters params(AudioParameters::AUDIO_PCM_LOW_LATENCY,
                           ChannelLayoutConfig::Stereo(), 48000, 2048);

    // Create a stream with the default device id "".
    AudioOutputStream* stream =
        audio_manager_->MakeAudioOutputStreamProxy(params, "");
    ASSERT_TRUE(stream);
    AudioOutputDispatcher* dispatcher1 =
        reinterpret_cast<AudioOutputProxy*>(stream)
            ->get_dispatcher_for_testing();

    // Closing this stream will put it up for reuse.
    stream->Close();
    stream = audio_manager_->MakeAudioOutputStreamProxy(
        params, AudioDeviceDescription::kDefaultDeviceId);

    // Verify both streams are created with the same dispatcher (which is unique
    // per device).
    ASSERT_EQ(dispatcher1, reinterpret_cast<AudioOutputProxy*>(stream)
                               ->get_dispatcher_for_testing());
    stream->Close();

    // Create a non-default device and ensure it gets a different dispatcher.
    stream = audio_manager_->MakeAudioOutputStreamProxy(params, "123456");
    ASSERT_NE(dispatcher1, reinterpret_cast<AudioOutputProxy*>(stream)
                               ->get_dispatcher_for_testing());
    stream->Close();
  }

  void GetDefaultOutputStreamParameters(media::AudioParameters* params) {
    *params = device_info_accessor_->GetDefaultOutputStreamParameters();
  }

  void GetAssociatedOutputDeviceID(const std::string& input_device_id,
                                   std::string* output_device_id) {
    *output_device_id =
        device_info_accessor_->GetAssociatedOutputDeviceID(input_device_id);
  }

 protected:
  AudioManagerTest() : message_loop_(base::MessagePumpType::IO) {
    CreateAudioManagerForTesting();
  }
  ~AudioManagerTest() override { audio_manager_->Shutdown(); }

  // Helper method which verifies that the device list starts with a valid
  // default record followed by non-default device names.
  static void CheckDeviceDescriptions(
      const AudioDeviceDescriptions& device_descriptions) {
    DVLOG(2) << "Got " << device_descriptions.size() << " audio devices.";
    if (!device_descriptions.empty()) {
      auto it = device_descriptions.begin();

      // The first device in the list should always be the default device.
      EXPECT_EQ(std::string(AudioDeviceDescription::kDefaultDeviceId),
                it->unique_id);
      ++it;

      // Other devices should have non-empty name and id and should not contain
      // default name or id.
      while (it != device_descriptions.end()) {
        EXPECT_FALSE(it->device_name.empty());
        EXPECT_FALSE(it->unique_id.empty());
        EXPECT_FALSE(it->group_id.empty());
        DVLOG(2) << "Device ID(" << it->unique_id
                 << "), label: " << it->device_name
                 << "group: " << it->group_id;
        EXPECT_NE(AudioDeviceDescription::GetDefaultDeviceName(),
                  it->device_name);
        EXPECT_NE(std::string(AudioDeviceDescription::kDefaultDeviceId),
                  it->unique_id);
        ++it;
      }
    } else {
      // Log a warning so we can see the status on the build bots.  No need to
      // break the test though since this does successfully test the code and
      // some failure cases.
      LOG(WARNING) << "No input devices detected";
    }
  }

  bool InputDevicesAvailable() {
#if BUILDFLAG(IS_MAC) && defined(ARCH_CPU_ARM64)
    // TODO(crbug.com/1128458): macOS on ARM64 says it has devices, but won't
    // let any of them be opened or listed.
    return false;
#else
    return device_info_accessor_->HasAudioInputDevices();
#endif
  }
  bool OutputDevicesAvailable() {
    return device_info_accessor_->HasAudioOutputDevices();
  }

  template <typename T = std::nullptr_t>
  void CreateAudioManagerForTesting() {
    // Only one AudioManager may exist at a time, so destroy the one we're
    // currently holding before creating a new one.
    // Flush the message loop to run any shutdown tasks posted by AudioManager.
    if (audio_manager_) {
      audio_manager_->Shutdown();
      device_info_accessor_.reset();
      audio_manager_.reset();
    }

    audio_manager_ =
        TestAudioManagerFactory<T>::Create(&fake_audio_log_factory_);
    // A few AudioManager implementations post initialization tasks to
    // audio thread. Flush the thread to ensure that |audio_manager_| is
    // initialized and ready to use before returning from this function.
    // TODO(alokp): We should perhaps do this in AudioManager::Create().
    base::RunLoop().RunUntilIdle();
    device_info_accessor_ =
        std::make_unique<AudioDeviceInfoAccessorForTests>(audio_manager_.get());
  }

  base::TestMessageLoop message_loop_;
  FakeAudioLogFactory fake_audio_log_factory_;
  std::unique_ptr<AudioManager> audio_manager_;
  std::unique_ptr<AudioDeviceInfoAccessorForTests> device_info_accessor_;
};

TEST_F(AudioManagerTest, HandleDefaultDeviceIDs) {
  // Use a fake manager so we can makeup device ids, this will still use the
  // AudioManagerBase code.
  CreateAudioManagerForTesting<FakeAudioManager>();
  HandleDefaultDeviceIDsTest();
  base::RunLoop().RunUntilIdle();
}

// Test that devices can be enumerated.
TEST_F(AudioManagerTest, EnumerateInputDevices) {
  ABORT_AUDIO_TEST_IF_NOT(InputDevicesAvailable());

  AudioDeviceDescriptions device_descriptions;
  device_info_accessor_->GetAudioInputDeviceDescriptions(&device_descriptions);
  CheckDeviceDescriptions(device_descriptions);
}

// Test that devices can be enumerated.
TEST_F(AudioManagerTest, EnumerateOutputDevices) {
  ABORT_AUDIO_TEST_IF_NOT(OutputDevicesAvailable());

  AudioDeviceDescriptions device_descriptions;
  device_info_accessor_->GetAudioOutputDeviceDescriptions(&device_descriptions);
  CheckDeviceDescriptions(device_descriptions);
}

// Run additional tests for Windows since enumeration can be done using
// two different APIs. MMDevice is default for Vista and higher and Wave
// is default for XP and lower.
#if BUILDFLAG(IS_WIN)

// Override default enumeration API and force usage of Windows MMDevice.
// This test will only run on Windows Vista and higher.
TEST_F(AudioManagerTest, EnumerateInputDevicesWinMMDevice) {
  ABORT_AUDIO_TEST_IF_NOT(InputDevicesAvailable());

  AudioDeviceDescriptions device_descriptions;
  device_info_accessor_->GetAudioInputDeviceDescriptions(&device_descriptions);
  CheckDeviceDescriptions(device_descriptions);
}

TEST_F(AudioManagerTest, EnumerateOutputDevicesWinMMDevice) {
  ABORT_AUDIO_TEST_IF_NOT(OutputDevicesAvailable());

  AudioDeviceDescriptions device_descriptions;
  device_info_accessor_->GetAudioOutputDeviceDescriptions(&device_descriptions);
  CheckDeviceDescriptions(device_descriptions);
}
#endif  // BUILDFLAG(IS_WIN)

#if defined(USE_PULSEAUDIO)
// On Linux, there are two implementations available and both can
// sometimes be tested on a single system. These tests specifically
// test Pulseaudio.

TEST_F(AudioManagerTest, EnumerateInputDevicesPulseaudio) {
  ABORT_AUDIO_TEST_IF_NOT(InputDevicesAvailable());

  CreateAudioManagerForTesting<AudioManagerPulse>();
  if (audio_manager_.get()) {
    AudioDeviceDescriptions device_descriptions;
    device_info_accessor_->GetAudioInputDeviceDescriptions(
        &device_descriptions);
    CheckDeviceDescriptions(device_descriptions);
  } else {
    LOG(WARNING) << "No pulseaudio on this system.";
  }
}

TEST_F(AudioManagerTest, EnumerateOutputDevicesPulseaudio) {
  ABORT_AUDIO_TEST_IF_NOT(OutputDevicesAvailable());

  CreateAudioManagerForTesting<AudioManagerPulse>();
  if (audio_manager_.get()) {
    AudioDeviceDescriptions device_descriptions;
    device_info_accessor_->GetAudioOutputDeviceDescriptions(
        &device_descriptions);
    CheckDeviceDescriptions(device_descriptions);
  } else {
    LOG(WARNING) << "No pulseaudio on this system.";
  }
}
#endif  // defined(USE_PULSEAUDIO)

#if defined(USE_ALSA)
// On Linux, there are two implementations available and both can
// sometimes be tested on a single system. These tests specifically
// test Alsa.

TEST_F(AudioManagerTest, EnumerateInputDevicesAlsa) {
  ABORT_AUDIO_TEST_IF_NOT(InputDevicesAvailable());

  DVLOG(2) << "Testing AudioManagerAlsa.";
  CreateAudioManagerForTesting<AudioManagerAlsa>();
  AudioDeviceDescriptions device_descriptions;
  device_info_accessor_->GetAudioInputDeviceDescriptions(&device_descriptions);
  CheckDeviceDescriptions(device_descriptions);
}

TEST_F(AudioManagerTest, EnumerateOutputDevicesAlsa) {
  ABORT_AUDIO_TEST_IF_NOT(OutputDevicesAvailable());

  DVLOG(2) << "Testing AudioManagerAlsa.";
  CreateAudioManagerForTesting<AudioManagerAlsa>();
  AudioDeviceDescriptions device_descriptions;
  device_info_accessor_->GetAudioOutputDeviceDescriptions(&device_descriptions);
  CheckDeviceDescriptions(device_descriptions);
}
#endif  // defined(USE_ALSA)

TEST_F(AudioManagerTest, GetDefaultOutputStreamParameters) {
#if BUILDFLAG(IS_WIN) || BUILDFLAG(IS_MAC)
  ABORT_AUDIO_TEST_IF_NOT(InputDevicesAvailable());

  AudioParameters params;
  GetDefaultOutputStreamParameters(&params);
  EXPECT_TRUE(params.IsValid());
#endif  // BUILDFLAG(IS_WIN) || BUILDFLAG(IS_MAC)
}

TEST_F(AudioManagerTest, GetAssociatedOutputDeviceID) {
#if BUILDFLAG(IS_WIN) || BUILDFLAG(IS_MAC)
  ABORT_AUDIO_TEST_IF_NOT(InputDevicesAvailable() && OutputDevicesAvailable());

  AudioDeviceDescriptions device_descriptions;
  device_info_accessor_->GetAudioInputDeviceDescriptions(&device_descriptions);
  bool found_an_associated_device = false;
  for (const auto& description : device_descriptions) {
    EXPECT_FALSE(description.unique_id.empty());
    EXPECT_FALSE(description.device_name.empty());
    EXPECT_FALSE(description.group_id.empty());
    std::string output_device_id;
    GetAssociatedOutputDeviceID(description.unique_id, &output_device_id);
    if (!output_device_id.empty()) {
      DVLOG(2) << description.unique_id << " matches with " << output_device_id;
      found_an_associated_device = true;
    }
  }

  EXPECT_TRUE(found_an_associated_device);
#endif  // BUILDFLAG(IS_WIN) || BUILDFLAG(IS_MAC)
}

class TestAudioManager : public FakeAudioManager {
  // For testing the default implementation of GetGroupId(Input|Output)
  // input$i is associated to output$i, if both exist.
  // Default input is input1.
  // Default output is output2.
 public:
  TestAudioManager(std::unique_ptr<AudioThread> audio_thread,
                   AudioLogFactory* audio_log_factory)
      : FakeAudioManager(std::move(audio_thread), audio_log_factory) {}

  std::string GetDefaultInputDeviceID() override {
    return kRealDefaultInputDeviceID;
  }
  std::string GetDefaultOutputDeviceID() override {
    return kRealDefaultOutputDeviceID;
  }
  std::string GetCommunicationsInputDeviceID() override {
    return kRealCommunicationsInputDeviceID;
  }
  std::string GetCommunicationsOutputDeviceID() override {
    return kRealCommunicationsOutputDeviceID;
  }

  std::string GetAssociatedOutputDeviceID(
      const std::string& input_id) override {
    if (input_id == "input1")
      return "output1";
    DCHECK_EQ(std::string(kRealDefaultInputDeviceID), "input2");
    if (input_id == AudioDeviceDescription::kDefaultDeviceId ||
        input_id == kRealDefaultInputDeviceID)
      return "output2";
    return std::string();
  }

 private:
  void GetAudioInputDeviceNames(AudioDeviceNames* device_names) override {
    DCHECK(device_names->empty());
    device_names->emplace_back(AudioDeviceName::CreateDefault());
    device_names->emplace_back("Input 1", "input1");
    device_names->emplace_back("Input 2", "input2");
    device_names->emplace_back("Input 3", "input3");
  }

  void GetAudioOutputDeviceNames(AudioDeviceNames* device_names) override {
    DCHECK(device_names->empty());
    device_names->emplace_back(AudioDeviceName::CreateDefault());
    device_names->emplace_back("Output 1", "output1");
    device_names->emplace_back("Output 2", "output2");
    device_names->emplace_back("Output 3", "output3");
  }
};

TEST_F(AudioManagerTest, GroupId) {
  CreateAudioManagerForTesting<TestAudioManager>();
  // Groups:
  // input1, output1
  // input2, output2, default input
  // input3
  // output3, default output
  AudioDeviceDescriptions inputs;
  device_info_accessor_->GetAudioInputDeviceDescriptions(&inputs);
  AudioDeviceDescriptions outputs;
  device_info_accessor_->GetAudioOutputDeviceDescriptions(&outputs);
  // default input
  EXPECT_EQ(inputs[0].group_id, outputs[2].group_id);
  // default input and default output are not associated
  EXPECT_NE(inputs[0].group_id, outputs[0].group_id);

  // default output
  EXPECT_EQ(outputs[0].group_id, outputs[3].group_id);

  // real inputs and outputs that are associated
  EXPECT_EQ(inputs[1].group_id, outputs[1].group_id);
  EXPECT_EQ(inputs[2].group_id, outputs[2].group_id);

  // real inputs and outputs that are not associated
  EXPECT_NE(inputs[3].group_id, outputs[3].group_id);

  // group IDs of different devices should differ.
  EXPECT_NE(inputs[1].group_id, inputs[2].group_id);
  EXPECT_NE(inputs[1].group_id, inputs[3].group_id);
  EXPECT_NE(inputs[2].group_id, inputs[3].group_id);
  EXPECT_NE(outputs[1].group_id, outputs[2].group_id);
  EXPECT_NE(outputs[1].group_id, outputs[3].group_id);
  EXPECT_NE(outputs[2].group_id, outputs[3].group_id);
}

TEST_F(AudioManagerTest, DefaultCommunicationsLabelsContainRealLabels) {
  CreateAudioManagerForTesting<TestAudioManager>();
  std::string default_input_id =
      device_info_accessor_->GetDefaultInputDeviceID();
  EXPECT_EQ(default_input_id, kRealDefaultInputDeviceID);
  std::string default_output_id =
      device_info_accessor_->GetDefaultOutputDeviceID();
  EXPECT_EQ(default_output_id, kRealDefaultOutputDeviceID);
  std::string communications_input_id =
      device_info_accessor_->GetCommunicationsInputDeviceID();
  EXPECT_EQ(communications_input_id, kRealCommunicationsInputDeviceID);
  std::string communications_output_id =
      device_info_accessor_->GetCommunicationsOutputDeviceID();
  EXPECT_EQ(communications_output_id, kRealCommunicationsOutputDeviceID);
  AudioDeviceDescriptions inputs;
  device_info_accessor_->GetAudioInputDeviceDescriptions(&inputs);
  CheckDescriptionLabels(inputs, default_input_id, communications_input_id);

  AudioDeviceDescriptions outputs;
  device_info_accessor_->GetAudioOutputDeviceDescriptions(&outputs);
  CheckDescriptionLabels(outputs, default_output_id, communications_output_id);
}

// GetPreferredOutputStreamParameters() can make changes to its input_params,
// ensure that creating a stream with the default parameters always works.
TEST_F(AudioManagerTest, CheckMakeOutputStreamWithPreferredParameters) {
  ABORT_AUDIO_TEST_IF_NOT(OutputDevicesAvailable());

  AudioParameters params;
  GetDefaultOutputStreamParameters(&params);
  ASSERT_TRUE(params.IsValid());

  AudioOutputStream* stream =
      audio_manager_->MakeAudioOutputStreamProxy(params, "");
  ASSERT_TRUE(stream);

  stream->Close();
}

#if BUILDFLAG(IS_MAC) || defined(USE_CRAS)
class TestAudioSourceCallback : public AudioOutputStream::AudioSourceCallback {
 public:
  TestAudioSourceCallback(int expected_frames_per_buffer,
                          base::WaitableEvent* event)
      : expected_frames_per_buffer_(expected_frames_per_buffer),
        event_(event) {}

  TestAudioSourceCallback(const TestAudioSourceCallback&) = delete;
  TestAudioSourceCallback& operator=(const TestAudioSourceCallback&) = delete;

  ~TestAudioSourceCallback() override {}

  int OnMoreData(base::TimeDelta,
                 base::TimeTicks,
                 const AudioGlitchInfo&,
                 AudioBus* dest) override {
    EXPECT_EQ(dest->frames(), expected_frames_per_buffer_);
    event_->Signal();
    return 0;
  }

  void OnError(ErrorType type) override { FAIL(); }

 private:
  const int expected_frames_per_buffer_;
  raw_ptr<base::WaitableEvent> event_;
};

// Test that we can create an AudioOutputStream with kMinAudioBufferSize and
// kMaxAudioBufferSize and that the callback AudioBus is the expected size.
TEST_F(AudioManagerTest, CheckMinMaxAudioBufferSizeCallbacks) {
  ABORT_AUDIO_TEST_IF_NOT(OutputDevicesAvailable());

#if BUILDFLAG(IS_MAC)
  CreateAudioManagerForTesting<AudioManagerMac>();
#elif defined(USE_CRAS) && BUILDFLAG(IS_CHROMEOS_ASH)
  CreateAudioManagerForTesting<AudioManagerCras>();
#endif

  DCHECK(audio_manager_);

  AudioParameters default_params;
  GetDefaultOutputStreamParameters(&default_params);
  ASSERT_LT(default_params.frames_per_buffer(),
            media::limits::kMaxAudioBufferSize);

#if BUILDFLAG(IS_MAC)
  // On OSX the preferred output buffer size is higher than the minimum
  // but users may request the minimum size explicitly.
  ASSERT_GT(default_params.frames_per_buffer(),
            GetMinAudioBufferSizeMacOS(media::limits::kMinAudioBufferSize,
                                       default_params.sample_rate()));
#elif defined(USE_CRAS)
  // On CRAS the preferred output buffer size varies per board and may be as low
  // as the minimum for some boards.
  ASSERT_GE(default_params.frames_per_buffer(),
            media::limits::kMinAudioBufferSize);
#else
  NOTREACHED();
#endif

  AudioOutputStream* stream;
  base::WaitableEvent event(base::WaitableEvent::ResetPolicy::AUTOMATIC,
                            base::WaitableEvent::InitialState::NOT_SIGNALED);

  // Create an output stream with the minimum buffer size parameters and ensure
  // that no errors are returned.
  AudioParameters min_params = default_params;
  min_params.set_frames_per_buffer(media::limits::kMinAudioBufferSize);
  stream = audio_manager_->MakeAudioOutputStreamProxy(min_params, "");
  ASSERT_TRUE(stream);
  EXPECT_TRUE(stream->Open());
  event.Reset();
  TestAudioSourceCallback min_source(min_params.frames_per_buffer(), &event);
  stream->Start(&min_source);
  event.Wait();
  stream->Stop();
  stream->Close();

  // Verify the same for the maximum buffer size.
  AudioParameters max_params = default_params;
  max_params.set_frames_per_buffer(media::limits::kMaxAudioBufferSize);
  stream = audio_manager_->MakeAudioOutputStreamProxy(max_params, "");
  ASSERT_TRUE(stream);
  EXPECT_TRUE(stream->Open());
  event.Reset();
  TestAudioSourceCallback max_source(max_params.frames_per_buffer(), &event);
  stream->Start(&max_source);
  event.Wait();
  stream->Stop();
  stream->Close();
}
#endif

}  // namespace media