The following example shows how to enumerate and select ltmmCapture object devices.
#include "ltmm.h" #include "resource.h" #include "tchar.h" #include "stdio.h" HINSTANCE g_hInstance; // application instance handle IltmmCapture* g_pCapture; // convert object's interface pointer // // BuildDeviceList // fills a listbox to match the contents of the collection // // pDevices = device collection's interface pointer // hwndListBox = listbox window handle // void BuildDeviceList(IltmmDevices* pDevices, HWND hwndListBox) { long i; long count; int selected = -1; // reset the listbox contents SendMessage(hwndListBox, LB_RESETCONTENT, 0, 0); // get the collection's item count pDevices->get_Count (&count); for(i = 0; i < count; i++) { IltmmDevice* pDevice; BSTR bstr; TCHAR sz[256]; int index; VARIANT_BOOL f; // retrieve collection item pDevices->Item (i, &pDevice); // get displayable name pDevice->get_FriendlyName (&bstr); // convert from unicode _stprintf(sz, _T("%ls"), bstr); // free name SysFreeString(bstr); // add the name to the listbox index = SendMessage(hwndListBox, LB_ADDSTRING, 0, (LPARAM) (LPCTSTR) sz); // associate the listbox item with the collection item index SendMessage(hwndListBox, LB_SETITEMDATA, index, i); // remember this listbox item, if it is selected in the collection pDevice->get_Selected (&f); if (f) selected = i; // free the collection item pDevice->Release(); } // select the appropriate listbox item for(i = 0; i < count; i++) { if (selected == (long) SendMessage(hwndListBox, LB_GETITEMDATA, i, 0)) { SendMessage(hwndListBox, LB_SETCURSEL, i, 0); break; } } } // // DeviceSelectionChanged // called to reflect changes in the listbox selection // // pDevices = device collection's interface pointer // hwndListBox = listbox window handle // void DeviceSelectionChanged(IltmmDevices* pDevices, HWND hwndListBox) { int index; long item; int i; int count; HRESULT hr; // get the index of current listbox selection index = (int) SendMessage(hwndListBox, LB_GETCURSEL, 0, 0); if (index < 0) { // clear selection pDevices->put_Selection (-1); } else { // get the collection item index item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0); // select the item #ifdef _DEBUG { IltmmDevice* pDevice; pDevices->Item (item, &pDevice); hr = pDevice->put_Selected(VARIANT_TRUE); pDevice->Release(); } #else hr = pDevices->put_Selection (item); #endif // if new selection failed, we need to force the listbox to match the actual selection if (FAILED(hr)) { // get the real selection pDevices->get_Selection (&item); // find the matching listbox item count = (int) SendMessage(hwndListBox, LB_GETCOUNT, 0, 0); for(i = 0; i < count; i++) { if (item == (long) SendMessage(hwndListBox, LB_GETITEMDATA, i, 0)) { SendMessage(hwndListBox, LB_SETCURSEL, i, 0); break; } } } } } // // RefreshDeviceList // called when to completely rebuild the collection // // pDevices = device collection's interface pointer // hwndListBox = listbox window handle // void RefreshDeviceList(IltmmDevices* pDevices, HWND hwndListBox) { IltmmDevice* pDevice; long item; BSTR bstr; // get the currently selected item pDevices->get_Selection (&item); if (item >= 0) { // get it's unique name pDevices->Item (item, &pDevice); pDevice->get_Name (&bstr); pDevice->Release(); } else { bstr = NULL; } // rebuild the collection pDevices->Refresh (); if (bstr) { // find the previously selected item pDevices->Find(bstr, &item); // make it the current selection if (item >= 0) pDevices->put_Selection (item); SysFreeString(bstr); } // rebuild the listbox BuildDeviceList(pDevices, hwndListBox); } // // DeviceDlgProc // selects object devices // BOOL CALLBACK DeviceDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) { IltmmDevices* pDevices; switch (msg) { case WM_INITDIALOG: // initialize the audio device listbox g_pCapture->get_AudioDevices (&pDevices); BuildDeviceList(pDevices, GetDlgItem(hwnd, IDC_AUDIODEVICES)); pDevices->Release(); // initialize the video device listbox g_pCapture->get_VideoDevices (&pDevices); BuildDeviceList(pDevices, GetDlgItem(hwnd, IDC_VIDEODEVICES)); pDevices->Release(); return TRUE; break; case WM_COMMAND: switch(LOWORD(wParam)) { case IDC_REFRESHAUDIODEVICES: // refresh the audio device listbox g_pCapture->get_AudioDevices (&pDevices); RefreshDeviceList(pDevices, GetDlgItem(hwnd, IDC_AUDIODEVICES)); pDevices->Release(); return TRUE; break; case IDC_AUDIODEVICES: if (HIWORD(wParam) == LBN_SELCHANGE) { // select the audio device g_pCapture->get_AudioDevices (&pDevices); DeviceSelectionChanged(pDevices, GetDlgItem(hwnd, IDC_AUDIODEVICES)); pDevices->Release(); } break; case IDC_REFRESHVIDEODEVICES: // initialize the video device listbox g_pCapture->get_VideoDevices (&pDevices); RefreshDeviceList(pDevices, GetDlgItem(hwnd, IDC_VIDEODEVICES)); pDevices->Release(); return TRUE; break; case IDC_VIDEODEVICES: if (HIWORD(wParam) == LBN_SELCHANGE) { // select the video device g_pCapture->get_VideoDevices (&pDevices); DeviceSelectionChanged(pDevices, GetDlgItem(hwnd, IDC_VIDEODEVICES)); pDevices->Release(); } break; case IDOK: EndDialog(hwnd, IDOK); return TRUE; break; } break; } return FALSE; } int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { HRESULT hr; g_hInstance = hInstance; // initialize COM library hr = CoInitialize(NULL); if (FAILED(hr)) goto error; // create the convert object hr = CoCreateInstance(CLSID_ltmmCapture, NULL, CLSCTX_INPROC_SERVER, IID_IltmmCapture, (void**) &g_pCapture); if (FAILED(hr)) goto error; DialogBox(g_hInstance, (LPCTSTR)IDD_DEVICEDLG, NULL, DeviceDlgProc); error: // cleanup if (g_pCapture) g_pCapture->Release(); CoUninitialize(); return 0; }