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# CreateRenderAudioStateMonitorForCategory

> CreateRenderAudioStateMonitorForCategory

# CreateRenderAudioStateMonitorForCategory

\[Some information relates to pre-released product which may be substantially modified before it's commercially released. Microsoft makes no warranties, express or implied, with respect to the information provided here.]

Creates a new instance of [IAudioStateMonitor](/reference/audio/audiostatemonitor/interfaces/iaudiostatemonitor) that monitors the audio level of all audio-rendering streams in the specified category.

## Syntax

```cpp theme={null}
HRESULT WINAPI CreateRenderAudioStateMonitorForCategory(
  AUDIO_STREAM_CATEGORY category,
  _Out_ IAudioStateMonitor **audioStateMonitor
);
```

### Parameters

*category*\
Type: AUDIO\_STREAM\_CATEGORY

A member of the <a href="https://learn.microsoft.com/en-us/windows/desktop/api/audiosessiontypes/ne-audiosessiontypes-audio_stream_category" target="_blank">AUDIO\_STREAM\_CATEGORY</a> enumeration that specifies the category of the audio-rendering streams to be monitored.

*audioStateMonitor* \_Out\_\
Type: IAudioStateMonitor\*\*

This output parameter is populated with the created `IAudioStateMonitor` object.

### Return value

Type: HRESULT

*category*
A member of the <a href="https://learn.microsoft.com/en-us/windows/desktop/api/audiosessiontypes/ne-audiosessiontypes-audio_stream_category">AUDIO\_STREAM\_CATEGORY</a> enumeration that specifies the category of audio render streams to be monitored.

*audioStateMonitor* \[out]
This output parameter is populated with the created `IAudioStateMonitor` object.

### Return Value

If the method succeeds, it returns `S\_OK`.

## Remarks

This is one of the functions that create and return an AudioStateMonitor instance.

There are four variants each for capture and render streams that determine
whether a process can do one of the following for a given role:

* Capture or render any audio of any category
* Capture or render audio of a specific category
* Capture or render audio of a specific category, to a specific endpoint.\
  The endpoint may be specified using the `MMDevice` ID (obtained using `IMMDevice::GetId()`), or by using its `SWD` ID (obtained using `Windows.Devices.Enumeration` or `Windows.Media.Devices.MediaDevice`)
* Capture or render audio of a specific category to the default endpoint

Consider the following scenario, where a game chooses to play GameMedia audio only when it is known that the audio will not be muted by the OS due to policy. To achieve this, the game registers for SoundLevel notifications for the [AudioCategory\_GameMedia](https://learn.microsoft.com/windows/desktop/api/audiosessiontypes/ne-audiosessiontypes-audio_stream_category) stream category on the default console endpoint. If the SoundLevel for this category is set to 'Muted' then the game will stop playback of its GameMedia stream. If the SoundLevel is set to anything else, the game chooses to play its GameMedia stream.

```cpp theme={null}
// 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. 
} 
```

## Requirements

**Header:** Audiostatemonitorapi.h

**Library:** Windows.Media.MediaControl.lib

**Supported platforms:** Windows, XBOX One family consoles and XBOX Series consoles

## See also

[AUDIO\_STREAM\_CATEGORY](https://learn.microsoft.com/windows/win32/api/audiosessiontypes/ne-audiosessiontypes-audio_stream_category)

[About WASAPI](https://learn.microsoft.com/windows/desktop/CoreAudio/wasapi)

[WASAPI](/build/console-features/audio/overviews/wasapi-overview)


## Related topics

- [IAudioStateMonitor interface](/reference/audio/audiostatemonitor/interfaces/iaudiostatemonitor.md)
- [AudioStateMonitor](/reference/audio/audiostatemonitor/audiostatemonitor_members.md)
- [CreateRenderAudioStateMonitorForCategoryAndDeviceId](/reference/audio/audiostatemonitor/functions/createrenderaudiostatemonitorforcategoryanddeviceid.md)
- [CreateRenderAudioStateMonitorForCategoryAndDeviceRole](/reference/audio/audiostatemonitor/functions/createrenderaudiostatemonitorforcategoryanddevicerole.md)
- [CreateRenderAudioStateMonitor](/reference/audio/audiostatemonitor/functions/createrenderaudiostatemonitor.md)