SetDefaultAudioPlaybackDevice.h

// This code comes from http://www.daveamenta.com/2011-05/programmatically-or-command-line-change-the-default-sound-playback-device-in-windows-7/
// License: MIT

#include "stdafx.h"
#include <Windows.h>
#include <mmdeviceapi.h>

#pragma once
interface DECLSPEC_UUID("f8679f50-850a-41cf-9c72-430f290290c8")
	IPolicyConfig;
class DECLSPEC_UUID("870af99c-171d-4f9e-af0d-e63df40c2bc9")
	CPolicyConfigClient;
interface IPolicyConfig : public IUnknown
{
public:

	virtual HRESULT GetMixFormat(
		PCWSTR,
		WAVEFORMATEX **
	);

	virtual HRESULT STDMETHODCALLTYPE GetDeviceFormat(
		PCWSTR,
		INT,
		WAVEFORMATEX **
	);

	virtual HRESULT STDMETHODCALLTYPE ResetDeviceFormat(
		PCWSTR
	);

	virtual HRESULT STDMETHODCALLTYPE SetDeviceFormat(
		PCWSTR,
		WAVEFORMATEX *,
		WAVEFORMATEX *
	);

	virtual HRESULT STDMETHODCALLTYPE GetProcessingPeriod(
		PCWSTR,
		INT,
		PINT64,
		PINT64
	);

	virtual HRESULT STDMETHODCALLTYPE SetProcessingPeriod(
		PCWSTR,
		PINT64
	);

	virtual HRESULT STDMETHODCALLTYPE GetShareMode(
		PCWSTR,
		struct DeviceShareMode *
	);

	virtual HRESULT STDMETHODCALLTYPE SetShareMode(
		PCWSTR,
		struct DeviceShareMode *
	);

	virtual HRESULT STDMETHODCALLTYPE GetPropertyValue(
		PCWSTR,
		const PROPERTYKEY&,
		PROPVARIANT *
	);

	virtual HRESULT STDMETHODCALLTYPE SetPropertyValue(
		PCWSTR,
		const PROPERTYKEY &,
		PROPVARIANT *
	);

	virtual HRESULT STDMETHODCALLTYPE SetDefaultEndpoint(
		__in PCWSTR wszDeviceId,
		__in ERole eRole
	);

	virtual HRESULT STDMETHODCALLTYPE SetEndpointVisibility(
		PCWSTR,
		INT
	);
};

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

	HRESULT hr = CoCreateInstance(__uuidof(CPolicyConfigClient),
		NULL, CLSCTX_ALL, __uuidof(IPolicyConfig), (LPVOID *)& pPolicyConfig);
	if (SUCCEEDED(hr))
	{
		hr = pPolicyConfig->SetDefaultEndpoint(devID, reserved);
		pPolicyConfig->Release();
	}
	return hr;
}