[ACCEPTED]-How to change default sound playback device programmatically?-mci

System Tray Audio Device Switcher uses "Software\Microsoft\Multimedia\Sound Mapper", "Playback" to 9 set the index of the sound device which 8 was obtained by enumeration the devices. mciSendCommand from 7 "winmm.dll" is also used

In this 6 source code you will find the registry keys 5 used to achieve that.

If this doesn't work 4 you could give Process Monitor a try and monitor all registry 3 activities of windows when you change the 2 default device. On my Vista installation 1 the control panel twiddles with "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\MMDevices\Audio\Render\"

For Vista see http://www.vistaaudiochanger.com/

There is no public API which allows you 12 to change the default audio device, that 11 is functionality that is considered to be 10 under the users control. This has always 9 been the case in Windows.

Having said that, if 8 you search the web, there are a number of 7 people who have reverse engineered the APIs 6 that are used in Windows Vista to do this, but 5 I'm not going to point you to them (the 4 reverse engineered APIs are internal unsupported 3 APIs and may change without notice from 2 Microsoft). You use these solutions at 1 your own peril.

I really don't know if anyone still needs 6 this, but here is my solution. Actually, it's 5 for the capture device, but it can be changed 4 easily to the render device.

It sets 3 registry 3 values in the device's key to the current 2 time. Magic, but that's how it works. Note: only 1 tested on Win7 x64

void SetDefaultRecordDevice(tstring strDeviceName){
    const int BUFF_LEN = 260;
    //HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\MMDevices\Audio\Capture\{79434968-09f6-4dff-8086-c5e618b21473}\Role:0:
    //"DE 07 08 00 06 00 10 00 15 00 38 00 1E 00 48 03"
    HKEY hkCaptureDevices;
    RegOpenKeyEx(HKEY_LOCAL_MACHINE, _T("SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\MMDevices\\Audio\\Capture") , 0, KEY_ENUMERATE_SUB_KEYS | KEY_WOW64_64KEY, &hkCaptureDevices);
    TCHAR lpwstrDeviceGuidKey[BUFF_LEN];
    DWORD dwDeviceGuidKeySize = BUFF_LEN;
    for(int i=0;RegEnumKeyEx(hkCaptureDevices, i, lpwstrDeviceGuidKey, &dwDeviceGuidKeySize, 0, 0, 0, 0) != ERROR_NO_MORE_ITEMS; ++i){
        dwDeviceGuidKeySize = BUFF_LEN;
        HKEY hkProps;
        RegOpenKeyEx(hkCaptureDevices, (tstring(lpwstrDeviceGuidKey) + _T("\\Properties")).c_str() , 0, KEY_READ | KEY_WOW64_64KEY, &hkProps);
        TCHAR data[BUFF_LEN];
        DWORD dwDataSize = BUFF_LEN;
        if(RegQueryValueEx(hkProps, _T("{a45c254e-df1c-4efd-8020-67d146a850e0},2"), 0, 0, (LPBYTE)data, &dwDataSize) !=  ERROR_SUCCESS){
            continue;
        } else {
            tstring strCurrentDeviceName(data);
            // TODO név általánosítás
            if(strDeviceName == strCurrentDeviceName){
                HKEY hkGuid;
                RegOpenKeyEx(hkCaptureDevices, lpwstrDeviceGuidKey , 0, KEY_READ | KEY_SET_VALUE | KEY_QUERY_VALUE | KEY_WOW64_64KEY | KEY_NOTIFY , &hkGuid);

                time_t CurrentTime;
                time(&CurrentTime);

                time_t     now = time(0);
                struct tm  tstruct;


                gmtime_s(&tstruct, &now);
                // Visit http://en.cppreference.com/w/cpp/chrono/c/strftime
                // for more information about date/time format

                char CustomRegistryDateValue[16];

                WORD year = tstruct.tm_year + 1900;
                WORD month = tstruct.tm_mon+1;
                WORD dayOfTheWeek = tstruct.tm_wday;
                WORD day = tstruct.tm_mday;
                WORD hour = tstruct.tm_hour;
                WORD minute = tstruct.tm_min;
                WORD second = tstruct.tm_sec;
                WORD millisec = 0x0; // hasrautés

                int k = 0;
                *((WORD*)CustomRegistryDateValue + k++) = year;
                *((WORD*)CustomRegistryDateValue + k++) = month;
                *((WORD*)CustomRegistryDateValue + k++) = dayOfTheWeek;
                *((WORD*)CustomRegistryDateValue + k++) = day;
                *((WORD*)CustomRegistryDateValue + k++) = hour;
                *((WORD*)CustomRegistryDateValue + k++) = minute;
                *((WORD*)CustomRegistryDateValue + k++) = second;
                *((WORD*)CustomRegistryDateValue + k++) = millisec;

                RegSetValueExA(hkGuid, ("Role:0"), 0, REG_BINARY, (LPBYTE)CustomRegistryDateValue, 16);
                RegSetValueExA(hkGuid, ("Role:1"), 0, REG_BINARY, (LPBYTE)CustomRegistryDateValue, 16);
                RegSetValueExA(hkGuid, ("Role:2"), 0, REG_BINARY, (LPBYTE)CustomRegistryDateValue, 16);
                RegFlushKey(hkGuid);
                RegCloseKey(hkGuid);
            }
        }
        RegCloseKey(hkProps);
    }
    RegCloseKey(hkCaptureDevices);
}