- 1 year ago
Setting MMDevice WaveFormat
To set the WaveFormat of an MMDevice (Multimedia Device) in Windows, you can use the Core Audio APIs provided by the Windows operating system. Here's a step-by-step approach to set the WaveFormat:
- Initialize COM: Before interacting with the Core Audio APIs, you need to initialize the COM library by calling the
CoInitializeEx
function. This is typically done at the beginning of your application.
cpp#include <comdef.h>
...
CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
Enumerate MMDevices: Use the
IMMDeviceEnumerator
interface to enumerate the MMDevices on the system and obtain the specific device you want to modify. You can use theEnumAudioEndpoints
method to enumerate the devices and theGetDefaultAudioEndpoint
method to obtain the default device or specific device by ID.Get the Device Property Store: Use the
IMMDevice::OpenPropertyStore
method to retrieve the property store of the device. The property store allows you to access and modify various properties of the device.Get the Format Property: Use the
IPropertyStore::GetValue
method to retrieve thePKEY_AudioEngine_DeviceFormat
property value from the property store. This property represents the current WaveFormat of the device.Modify the Format: Modify the retrieved WaveFormat as desired. You can change the sample rate, bit depth, channel configuration, etc. of the format.
Set the Format Property: Use the
IPropertyStore::SetValue
method to set the modified WaveFormat back to the property store using thePKEY_AudioEngine_DeviceFormat
property.Commit Changes: Call the
IPropertyStore::Commit
method to commit the changes made to the property store.Release Resources: Release all acquired COM interfaces and resources to properly clean up.
Here's a sample code snippet in C++ demonstrating the above steps:
cpp#include <comdef.h>
#include <mmdeviceapi.h>
#include <endpointvolume.h>
void SetMMDeviceWaveFormat()
{
CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
IMMDeviceEnumerator* pEnumerator = NULL;
IMMDevice* pDevice = NULL;
IPropertyStore* pPropertyStore = NULL;
// Step 1: Enumerate MMDevices
CoCreateInstance(
__uuidof(MMDeviceEnumerator),
NULL,
CLSCTX_ALL,
__uuidof(IMMDeviceEnumerator),
(LPVOID*)&pEnumerator
);
pEnumerator->GetDefaultAudioEndpoint(eRender, eConsole, &pDevice);
// Step 2: Get the Device Property Store
pDevice->OpenPropertyStore(STGM_READWRITE, &pPropertyStore);
// Step 3: Get the Format Property
PROPVARIANT propValue;
PropVariantInit(&propValue);
pPropertyStore->GetValue(PKEY_AudioEngine_DeviceFormat, &propValue);
// Step 4: Modify the Format
WAVEFORMATEX* pWaveFormat = reinterpret_cast<WAVEFORMATEX*>(propValue.blob.pBlobData);
// Modify the WaveFormat as desired
// Step 5: Set the Format Property
pPropertyStore->SetValue(PKEY_AudioEngine_DeviceFormat, &propValue);
// Step 6: Commit Changes
pPropertyStore->Commit();
PropVariantClear(&propValue);
// Step 8: Release Resources
pPropertyStore->Release();
pDevice->Release();
pEnumerator->Release();
CoUninitialize();
}
Note: Make sure to link against the required libraries (ole32.lib
, uuid.lib
, etc.) and include the necessary header files (comdef.h
, mmdeviceapi.h
, etc.) in your project.
Please adjust the code based on your specific requirements and error handling needs.