Getting and Setting Microphone Gain or Microphone Boost on Windows 7 / 8 Programmatically

After hours of searching the net I have finally figured out a way to programmatically get and set the microphone gain (boost) value.

The code mentioned below can be built on VS and does the job of setting gain value.


#include "stdafx.h"
#include <mmdeviceapi.h>
#include <endpointvolume.h>
#include <Functiondiscoverykeys_devpkey.h>
#include "Audioclient.h"
#include "comutil.h"

#define EXIT_ON_ERROR(hres)   if (FAILED(hres)) { goto Exit; }
#define SAFE_RELEASE(punk)   if ((punk) != NULL)  { (punk)->Release(); (punk) = NULL; }

HRESULT getMicrophoneBoostVolumeLevel(IMMDevice *pEndptDev, IAudioVolumeLevel** ppVolumeLevel)
{
HRESULT hr = S_OK;
DataFlow flow;
IDeviceTopology *pDeviceTopology = NULL;
IConnector *pConnFrom = NULL;
IConnector *pConnTo = NULL;
IPart *pPartPrev = NULL;
IPart *pPartNext = NULL;
*ppVolumeLevel = NULL;
wchar_t microphoneBoostName[] = L"Microphone Boost";//if your system language is English,the name is "microphone boost"
if (pEndptDev == NULL)
{
EXIT_ON_ERROR(hr = E_POINTER)
}

// Get the endpoint device's IDeviceTopology interface.
hr = pEndptDev->Activate(
__uuidof(IDeviceTopology), CLSCTX_ALL, NULL,
(void**)&pDeviceTopology);
EXIT_ON_ERROR(hr)
// The device topology for an endpoint device always
// contains just one connector (connector number 0).
hr = pDeviceTopology->GetConnector(0, &pConnFrom);
SAFE_RELEASE(pDeviceTopology)
EXIT_ON_ERROR(hr)
// Make sure that this is a capture device.
hr = pConnFrom->GetDataFlow(&flow);
EXIT_ON_ERROR(hr)
if (flow != Out)
{
// Error -- this is a rendering device.
//EXIT_ON_ERROR(hr = AUDCLNT_E_WRONG_ENDPOINT_TYPE)
}
// Outer loop: Each iteration traverses the data path
// through a device topology starting at the input
// connector and ending at the output connector.
while (TRUE)
{
BOOL bConnected;
hr = pConnFrom->IsConnected(&bConnected);
EXIT_ON_ERROR(hr)
// Does this connector connect to another device?
if (bConnected == FALSE)
{
// This is the end of the data path that
// stretches from the endpoint device to the
// system bus or external bus. Verify that
// the connection type is Software_IO.
ConnectorType  connType;
hr = pConnFrom->GetType(&connType);
EXIT_ON_ERROR(hr)
if (connType == Software_IO)
{
break;  // finished
}
EXIT_ON_ERROR(hr = E_FAIL)
}
// Get the connector in the next device topology,
// which lies on the other side of the connection.
hr = pConnFrom->GetConnectedTo(&pConnTo);
EXIT_ON_ERROR(hr)
SAFE_RELEASE(pConnFrom)
// Get the connector's IPart interface.
hr = pConnTo->QueryInterface(
__uuidof(IPart), (void**)&pPartPrev);
EXIT_ON_ERROR(hr)
SAFE_RELEASE(pConnTo)
// Inner loop: Each iteration traverses one link in a
// device topology and looks for input multiplexers.
while (TRUE)
{
PartType parttype;
IPartsList *pParts;
// Follow downstream link to next part.
hr = pPartPrev->EnumPartsOutgoing(&pParts);
EXIT_ON_ERROR(hr)
hr = pParts->GetPart(0, &pPartNext);
pParts->Release();
EXIT_ON_ERROR(hr)
hr = pPartNext->GetPartType(&parttype);
EXIT_ON_ERROR(hr)

LPWSTR pName;
if (SUCCEEDED(pPartNext->GetName(&pName)))
{
// Failure of the following call means only that
// the part is not a boost (micrphone boost).
if (wcscmp(microphoneBoostName, pName) == 0)
{
//get IAudioVolumeLevel to control volume
hr = pPartNext->Activate(CLSCTX_ALL, __uuidof(IAudioVolumeLevel), (void**)ppVolumeLevel);
goto Exit;
}
CoTaskMemFree(pName);
}
GUID subType;
pPartNext->GetSubType(&subType);
if (parttype == Connector)
{
// We've reached the output connector that
// lies at the end of this device topology.
hr = pPartNext->QueryInterface(
__uuidof(IConnector),
(void**)&pConnFrom);
EXIT_ON_ERROR(hr)
SAFE_RELEASE(pPartPrev)
SAFE_RELEASE(pPartNext)
break;
}
SAFE_RELEASE(pPartPrev)
pPartPrev = pPartNext;
pPartNext = NULL;
}
}
Exit:
SAFE_RELEASE(pConnFrom)
SAFE_RELEASE(pConnTo)
SAFE_RELEASE(pPartPrev)
SAFE_RELEASE(pPartNext)
return hr;
}

int setMicrophoneBoost(bool bIsBoost, bool bIsIncrease) {
HRESULT hr = NULL;
CoInitialize(NULL);

IMMDeviceEnumerator *deviceEnumerator = NULL;

hr = CoCreateInstance(__uuidof(MMDeviceEnumerator), NULL, CLSCTX_INPROC_SERVER,
__uuidof(IMMDeviceEnumerator), (LPVOID *)&deviceEnumerator);

IMMDevice *defaultDevice = NULL;

if (hr != S_OK)
{
return 0;
}

hr = deviceEnumerator->GetDefaultAudioEndpoint(eCapture, eMultimedia, &defaultDevice);
deviceEnumerator->Release();

deviceEnumerator = NULL;

IAudioVolumeLevel* pIaudioVolumeLevel;
getMicrophoneBoostVolumeLevel(defaultDevice, &pIaudioVolumeLevel);

defaultDevice->Release();
defaultDevice = NULL;

if (pIaudioVolumeLevel == NULL)
{
return 0;
}

if (bIsBoost)
{
float fMinDb;
float fMaxDb;
float fStepDb;
float pfCurrentDb = 0.0f;
pIaudioVolumeLevel->GetLevelRange(0, &fMinDb, &fMaxDb, &fStepDb);

pIaudioVolumeLevel->GetLevel(0, &pfCurrentDb);
if (bIsIncrease) {
if (pfCurrentDb < fMaxDb) {
pfCurrentDb += fStepDb; // Incrementing DB level By stepincrement
pIaudioVolumeLevel->SetLevel(0, pfCurrentDb, NULL);
}
}
else {
if (pfCurrentDb > fMinDb) {
pfCurrentDb -= fStepDb; // Decrementing DB level By stepincrement
pIaudioVolumeLevel->SetLevel(0, pfCurrentDb, NULL);
}
}
}

return 0;
}

int _tmain(int argc, _TCHAR* argv[])
{
int choice;
printf("\r\n Choose 1: to increment gain \r\n Choose 2: to decrement gain \r\n else press any key to return \r\n");
scanf_s("%d", &choice);

switch (choice) {
case 1:
setMicrophoneBoost(true, true); // incrementing db level
break;
case 2:
setMicrophoneBoost(true, false); // decrementing db level
break;
default:
printf("Keeping the microphone gain as is!!!");
break;
}
return 0;
}



User choices are simple, Run the exe from command prompt, enter 1 to increase the microphone boost DB value or 2 to decrease the same.