Essa enumeração é usada pelo método IAudioStateMonitor::GetSoundLevel.Considere o cenário a seguir, em que um jogo opta por reproduzir áudio GameMedia somente quando se sabe que o áudio não será silenciado pelo sistema operacional devido a uma política. Para isso, o jogo se registra para receber notificações de SoundLevel para a categoria de fluxo AudioCategory_GameMedia no ponto de extremidade padrão do console. Se o SoundLevel dessa categoria for definido como ‘Muted’, o jogo interromperá a reprodução do seu fluxo GameMedia. Se o SoundLevel for definido como qualquer outro valor, o jogo optará por reproduzir seu fluxo GameMedia.
// global variables winrt::com_ptr<IAudioStateMonitor> g_audioStateMonitor; AudioStateMonitorRegistrationHandle g_registration = 0; // Returns true if the GameMedia stream should be disabled, false if it should be // enabled. bool IsSoundLevelMuted(_In_ IAudioStateMonitor* audioStateMonitor) { return (audioStateMonitor->GetSoundLevel() == AudioStateMonitorSoundLevel::Muted); } HRESULT StartTrackingSoundLevel() { // Create an AudioStateMonitor and register for callbacks from it. HRESULT hr = RegisterForSoundLevelChanges(); if (SUCCEEDED(hr)) { // Check the current sound level and determine if the GameMedia stream should // be enabled. bool disableGameMediaStream = IsSoundLevelMuted(g_audioStateMonitor.get()); // Add code here that enables or disables the GameMedia stream based on the // value of the boolean. } return hr; } HRESULT RegisterForSoundLevelChanges() { HRESULT hr = S_OK; // Create a new AudioStateMonitor for the GameMedia category, if needed, and // register for callbacks. if (m_audioStateMonitor == nullptr) { hr = CreateRenderAudioStateMonitorForCategoryAndDeviceRole( AudioCategory_GameMedia, ERole::eConsole, g_audioStateMonitor.put()); if (SUCCEEDED(hr)) { // Optional "context" parameter is not used in this example, // and is set to nullptr. hr = g_audioStateMonitor->RegisterCallback(OnAudioStateMonitorCallback, nullptr, &g_registration); } } if (FAILED(hr)) { // g_audioStateMonitor is a smart pointer, so if an IAudioStateMonitor was // allocated, setting the smart pointer to null invokes the Release method // which will decrement its usage count and ensure that the object is properly // destroyed. g_audioStateMonitor = nullptr; } return hr; } // Unregister callbacks on program shutdown void UnregisterForSoundLevelChanges() { if (g_audioStateMonitor != nullptr) { if (g_registration) { g_audioStateMonitor->UnregisterCallback(g_registration); } // g_audioStateMonitor is a smart pointer, so setting it to null // invokes the Release method to decrement its usage count. g_audioStateMonitor = nullptr; } } void OnAudioStateMonitorCallback(_In_ IAudioStateMonitor* audioStateMonitor, _In_opt_ void* context) { bool disableGameMediaStream = IsSoundLevelMuted(audioStateMonitor); // Add code here that enables or disables the GameMedia stream based on the value // of the boolean. }
