Selecting ltmmCapture Object Inputs for C

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(); 
} 

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