How to get audio session GUID with Windows API - c++

Question

I'm trying to make a simple mixer app using Windows audio API. I've already figured out how to get IAudioSessionEnumerator and IAudioSessionControl which allows me to retrieve the DisplayName of each session. And now I want to get/set volumes of these sessions. From winApi docs I think I first need to use GetSimpleAudioVolume method but it requires session GUID as a parameter. So how do I get a GUID of an existing session? I couldn't find any answers for that in docs or google. Or maybe I missunderstood something?
//code prints DisplayNames of all sessions
void getSessions() {
CoInitialize(NULL);
IMMDeviceEnumerator *pDEnumerator = NULL;
CoCreateInstance(CLSID_MMDeviceEnumerator, NULL, CLSCTX_ALL, IID_IMMDeviceEnumerator, (void**)&pDEnumerator);
IMMDevice *pDevice = NULL;
pDEnumerator->GetDefaultAudioEndpoint(eRender, eMultimedia, &pDevice);
IAudioSessionManager2 *pSManager2 = NULL;
pDevice->Activate(IID_IAudioSessionManager2, CLSCTX_ALL, NULL, (void**)&pSManager2);
IAudioSessionEnumerator *pSEnumerator = NULL;
pSManager2->GetSessionEnumerator(&pSEnumerator);
int audioSessionCount;
pSEnumerator->GetCount(&audioSessionCount);
std::cout << audioSessionCount << '\n';
for (int i = 0; i < audioSessionCount; ++i) {
IAudioSessionControl *controls;
pSEnumerator->GetSession(i, &controls);
LPWSTR name;
controls->GetDisplayName(&name);
while (*name != 0) {
std::wcout << *name;
++name;
}
std::cout << '\n';
}
}

Answer 1

Each audio session is uniquely identified with a GUID—session instance
identifier.
You can IAudioSessionControl2::GetSessionInstanceIdentifier and retrieve a string that contains the session identifier.
Or you can query ISimpleAudioVolume interface on IAudioSessionControl interface like this:
ISimpleAudioVolume *simpleAudioVol = NULL;
controls->QueryInterface(IID_PPV_ARGS(&simpleAudioVol));