Programmatically switch audio devices on Windows 7

Question

On my Windows 7 PC, I\'ve got a set of speakers, some wireless headphones and a USB web cam. This means that I have two possible audio output devices and 2 possible audio in

Answer 1

If you are looking into changing default devices programmatically, then this is impossible by design.

• Programatically setting the default playback device (and recording device)
• How to change default sound playback device programatically?

Answer 2

Allegedly undocumented COM-interface IPolicyConfig (kudos to @author EreTIk) allows to do that.

This is a sample implementation.

HRESULT SetDefaultAudioPlaybackDevice(LPCWSTR devID)
{
    IPolicyConfigVista *pPolicyConfig;
    ERole reserved = eConsole;

    HRESULT hr = CoCreateInstance(
                    __uuidof(CPolicyConfigVistaClient),
                    NULL, 
                    CLSCTX_ALL, 
                    __uuidof(IPolicyConfigVista), 
                    (LPVOID *)&pPolicyConfig);

    if (SUCCEEDED(hr))
    {
        hr = pPolicyConfig->SetDefaultEndpoint(devID, reserved);
        pPolicyConfig->Release();
    }

    return hr;
}

A string of Device ID needs to be passed to this function. An example of a device id

{0.0.1.00000000}.{d915c7bb-d5d7-4c92-80d9-1a0ee5d954f1}

This device id can be obtained through audio device enumeration.