The following example shows how to enumerate and select ltmmCapture object inputs.
// define helper macros for using interfaces under C #ifndef COBJMACROS #define COBJMACROS #endif #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 // // BuildCaptureInputList // fills a listbox to match the contents of the collection // // pCaptureInputs = input collection's interface pointer // hwndListBox = listbox window handle // void BuildCaptureInputList(IltmmCaptureInputs* pCaptureInputs, 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 IltmmCaptureInputs_get_Count (pCaptureInputs, &count); for(i = 0; i < count; i++) { IltmmCaptureInput* pCaptureInput; BSTR bstr; TCHAR sz[256]; int index; VARIANT_BOOL f; // retrieve collection item IltmmCaptureInputs_Item (pCaptureInputs, i, &pCaptureInput); // get displayable name IltmmCaptureInput_get_Name (pCaptureInput, &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 IltmmCaptureInput_get_Selected (pCaptureInput, &f); if(f) selected = i; // free the collection item IUnknown_Release(pCaptureInput); } // 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; } } } // // CaptureInputSelectionChanged // called to reflect changes in the listbox selection // // pCaptureInputs = input collection's interface pointer // hwndListBox = listbox window handle // void CaptureInputSelectionChanged(IltmmCaptureInputs* pCaptureInputs, 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 IltmmCaptureInputs_put_Selection (pCaptureInputs, -1); } else { // get the collection item index item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0); // select the item #ifdef _DEBUG { IltmmCaptureInput* pCaptureInput; IltmmCaptureInputs_Item (pCaptureInputs, item, &pCaptureInput); hr = IltmmCaptureInput_put_Selected (pCaptureInput, VARIANT_TRUE); IUnknown_Release(pCaptureInput); } #else hr = IltmmCaptureInputs_put_Selection (pCaptureInputs, item); #endif // if new selection failed, we need to force the listbox to match the actual selection if(FAILED(hr)) { // get the real selection IltmmCaptureInputs_get_Selection (pCaptureInputs, &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; } } } } } // // SelectCompositeVideo // selects composite video, if available // // pCaptureInputs = input collection's interface pointer // hwndListBox = listbox window handle // void SelectCompositeVideo(IltmmCaptureInputs* pCaptureInputs, HWND hwndListBox) { long item; BSTR bstr; long i; long count; // Find the composite video input bstr = SysAllocString(L"Video Composite"); IltmmCaptureInputs_Find(pCaptureInputs, bstr, &item); SysFreeString(bstr); // make it the current selection if(item >= 0) { IltmmCaptureInputs_put_Selection (pCaptureInputs, item); IltmmCaptureInputs_get_Count (pCaptureInputs, &count); // select the appropriate listbox item for(i = 0; i < count; i++) { if(item == (long) SendMessage(hwndListBox, LB_GETITEMDATA, i, 0)) { SendMessage(hwndListBox, LB_SETCURSEL, i, 0); break; } } } } // // CaptureInputDlgProc // selects object inputs // BOOL CALLBACK CaptureInputDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) { IltmmCaptureInputs* pCaptureInputs; wParam = wParam ; lParam = lParam ; switch (msg) { case WM_INITDIALOG: // initialize the video input listbox IltmmCapture_get_VideoInputs (g_pCapture, &pCaptureInputs); BuildCaptureInputList(pCaptureInputs, GetDlgItem(hwnd, IDC_VIDEOINPUTS)); IUnknown_Release(pCaptureInputs); return TRUE; break; case WM_COMMAND: switch(LOWORD(wParam)) { case IDC_SELECTCOMPOSITEVIDEO: // select composite video IltmmCapture_get_VideoInputs (g_pCapture, &pCaptureInputs); SelectCompositeVideo(pCaptureInputs, GetDlgItem(hwnd, IDC_VIDEOINPUTS)); IUnknown_Release(pCaptureInputs); return TRUE; break; case IDC_VIDEOINPUTS: if(HIWORD(wParam) == LBN_SELCHANGE) { // select the video input IltmmCapture_get_VideoInputs (g_pCapture, &pCaptureInputs); CaptureInputSelectionChanged(pCaptureInputs, GetDlgItem(hwnd, IDC_VIDEOINPUTS)); IUnknown_Release(pCaptureInputs); } break; case IDOK: EndDialog(hwnd, IDOK); return TRUE; break; } break; } return FALSE; } void SelectingltmmCaptureObjectInputs_Example ( HINSTANCE hInstance /*application instance handle*/ ) { HRESULT hr; IltmmDevices* pDevices; g_hInstance = hInstance; // initialize COM library hr = CoInitialize(NULL); if(FAILED(hr)) goto error; // create the capture object hr = CoCreateInstance(&CLSID_ltmmCapture, NULL, CLSCTX_INPROC_SERVER, &IID_IltmmCapture, (void**) &g_pCapture); if(FAILED(hr)) goto error; // select the first audio device available IltmmCapture_get_AudioDevices (g_pCapture, &pDevices); IltmmDevices_put_Selection (pDevices, 0); IUnknown_Release(pDevices); // select the first video device available IltmmCapture_get_VideoDevices (g_pCapture, &pDevices); IltmmDevices_put_Selection (pDevices, 0); IUnknown_Release(pDevices); DialogBox(g_hInstance, (LPCTSTR)IDD_INPUTDLG, NULL, CaptureInputDlgProc); error: // cleanup if(g_pCapture) IUnknown_Release(g_pCapture); CoUninitialize(); }