GetSimpleAudioVolume

AudioDeviceWindowsCore

GetSimpleAudioVolume 返回值赋值到 _ptrRenderSimpleVolume

源码分析

h:\webrtc-20210315\webrtc-20210315\webrtc\webrtc-checkout\src\media\engine\webrtc_voice_engine.cc

WebRtcVoiceEngine::Init

void WebRtcVoiceEngine::Init() {
***
  RTC_CHECK(adm());
  webrtc::adm_helpers::Init(adm());
***
}

这时候进入到
H:\webrtc-20210315\webrtc-20210315\webrtc\webrtc-checkout\src\media\engine\adm_helpers.cc
void Init(AudioDeviceModule adm) 方法
这时候进入到
H:\webrtc-20210315\webrtc-20210315\webrtc\webrtc-checkout\src\media\engine\adm_helpers.cc
void Init(AudioDeviceModule adm) 方法

webrtc::adm_helpers::Init

void Init(AudioDeviceModule* adm) {
  RTC_DCHECK(adm);
****
  // Playout device.
  {
    if (adm->SetPlayoutDevice(AUDIO_DEVICE_ID) != 0) {
      RTC_LOG(LS_ERROR) << "Unable to set playout device.";
      return;
    }
    if (adm->InitSpeaker() != 0) {
      RTC_LOG(LS_ERROR) << "Unable to access speaker.";
    }
***
}

这里主要讲 adm->InitSpeaker().

AudioDeviceModuleImpl::InitSpeaker

int32_t AudioDeviceModuleImpl::InitSpeaker() {
  RTC_LOG(INFO) << __FUNCTION__;
  CHECKinitialized_();
  return audio_device_->InitSpeaker();
}

AudioDeviceWindowsCore::InitSpeaker

int32_t AudioDeviceWindowsCore::InitSpeaker() {
  MutexLock lock(&mutex_);
  return InitSpeakerLocked();
}

AudioDeviceWindowsCore::InitSpeakerLocked

int32_t AudioDeviceWindowsCore::InitSpeakerLocked() {
  if (_playing) {
    return -1;
  }
  if (_ptrDeviceOut == NULL) {
    return -1;
  }
  if (_usingOutputDeviceIndex) {
    int16_t nDevices = PlayoutDevicesLocked();
    if (_outputDeviceIndex > (nDevices - 1)) {
      RTC_LOG(LS_ERROR) << "current device selection is invalid => unable to"
                           " initialize";
      return -1;
    }
  }
  int32_t ret(0);
  SAFE_RELEASE(_ptrDeviceOut);
  if (_usingOutputDeviceIndex) {
    // Refresh the selected rendering endpoint device using current index
    ret = _GetListDevice(eRender, _outputDeviceIndex, &_ptrDeviceOut);
  } else {
    ERole role;
    (_outputDevice == AudioDeviceModule::kDefaultDevice)
        ? role = eConsole
        : role = eCommunications;
    // Refresh the selected rendering endpoint device using role
      // 里面会调用 _ptrEnumerator->GetDefaultAudioEndpoint(dir, role, ppDevice)
      // 刷新是必须的，避免操作时设备已经没有了。
    ret = _GetDefaultDevice(eRender, role, &_ptrDeviceOut);
  }
  if (ret != 0 || (_ptrDeviceOut == NULL)) {
    RTC_LOG(LS_ERROR) << "failed to initialize the rendering enpoint device";
    SAFE_RELEASE(_ptrDeviceOut);
    return -1;
  }
  IAudioSessionManager* pManager = NULL;
  ret = _ptrDeviceOut->Activate(__uuidof(IAudioSessionManager), CLSCTX_ALL,
                                NULL, (void**)&pManager);
  if (ret != 0 || pManager == NULL) {
    RTC_LOG(LS_ERROR) << "failed to initialize the render manager";
    SAFE_RELEASE(pManager);
    return -1;
  }
//通过上面的pManager来获取操作音频音量对象，NULL音频流使用默认session，FALSE非跨进程
  SAFE_RELEASE(_ptrRenderSimpleVolume);
  ret = pManager->GetSimpleAudioVolume(NULL, FALSE, &_ptrRenderSimpleVolume);
  if (ret != 0 || _ptrRenderSimpleVolume == NULL) {
    RTC_LOG(LS_ERROR) << "failed to initialize the render simple volume";
    SAFE_RELEASE(pManager);
    SAFE_RELEASE(_ptrRenderSimpleVolume);
    return -1;
  }
  SAFE_RELEASE(pManager);
  _speakerIsInitialized = true;
  return 0;
}

堆栈调用