Selecting ltmmCapture Object Compressors for C++

#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 
 
// 
// BuildCompressorList 
// fills a listbox to match the contents of the collection 
// 
// pCompressors = compressor collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void BuildCompressorList(IltmmCompressors* pCompressors, 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 
   pCompressors->get_Count (&count);  
 
   for(i = 0; i < count; i++) 
   { 
      IltmmCompressor* pCompressor;  
      BSTR bstr;  
      TCHAR sz[256];  
      int index;  
      VARIANT_BOOL f;  
 
      // retrieve collection item 
      pCompressors->Item(i, &pCompressor);  
    
      // get displayable name 
      pCompressor->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 
      pCompressor->get_Selected (&f);  
      if (f)  
         selected = i;  
    
      // free the collection item 
      pCompressor->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;  
      } 
   } 
 
} 
 
// 
// CompressorSelectionChanged 
// called to reflect changes in the listbox selection 
// 
// pCompressors = compressor collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void CompressorSelectionChanged(IltmmCompressors* pCompressors, 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 
      pCompressors->put_Selection (-1);  
   } 
   else 
   { 
 
      // get the collection item index 
      item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0);  
    
      // select the item 
#ifdef _DEBUG 
      { 
         IltmmCompressor* pCompressor;  
         pCompressors->Item (item, &pCompressor);  
         hr = pCompressor->put_Selected (VARIANT_TRUE);  
         pCompressor->Release(); 
      } 
#else 
      hr = pCompressors->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 
         pCompressors->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;  
            } 
         } 
 
      } 
    
   } 
 
} 
 
// 
// RefreshCompressorList 
// called when to completely rebuild the collection 
// 
// pCompressors = compressor collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void RefreshCompressorList(IltmmCompressors* pCompressors, HWND hwndListBox)  
{ 
   IltmmCompressor* pCompressor;  
   long item;  
   BSTR bstr;  
 
 
   // get the currently selected item    
   pCompressors->get_Selection (&item);  
 
   if (item >= 0)  
   { 
      // get it's unique name 
      pCompressors->Item (item, &pCompressor);  
      pCompressor->get_Name (&bstr);  
      pCompressor->Release(); 
   } 
   else 
   { 
      bstr = NULL;  
   } 
 
   // rebuild the collection 
   pCompressors->Refresh (); 
    
   if (bstr)  
   { 
      // find the previously selected item 
      pCompressors->Find (bstr, &item);  
 
      // make it the current selection 
      if (item >= 0)  
         pCompressors->put_Selection (item); 
          
      SysFreeString(bstr);  
   } 
 
   // rebuild the listbox 
   BuildCompressorList(pCompressors, hwndListBox);  
} 
 
// 
// CompressorDlgProc 
// selects object compressors 
// 
BOOL CALLBACK CompressorDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)  
{ 
   IltmmCompressors* pCompressors;  
    
   switch (msg)  
   { 
   case WM_INITDIALOG:  
      // initialize the audio compressor listbox 
      g_pCapture->get_AudioCompressors (&pCompressors);  
      BuildCompressorList(pCompressors, GetDlgItem(hwnd, IDC_AUDIOCOMPRESSORS));  
      pCompressors->Release(); 
 
      // initialize the video compressor listbox 
      g_pCapture->get_VideoCompressors (&pCompressors);  
      BuildCompressorList(pCompressors, GetDlgItem(hwnd, IDC_VIDEOCOMPRESSORS));  
      pCompressors->Release(); 
       
      return TRUE;  
      break;  
 
   case WM_COMMAND:  
      switch(LOWORD(wParam))  
      { 
      case IDC_REFRESHAUDIOCOMPRESSORS:  
         // refresh the audio compressor listbox 
         g_pCapture->get_AudioCompressors (&pCompressors);  
         RefreshCompressorList(pCompressors, GetDlgItem(hwnd, IDC_AUDIOCOMPRESSORS));  
         pCompressors->Release(); 
         return TRUE;  
         break;  
      case IDC_AUDIOCOMPRESSORS:  
         if (HIWORD(wParam) == LBN_SELCHANGE)  
         { 
            // select the audio compressor 
            g_pCapture->get_AudioCompressors (&pCompressors);  
            CompressorSelectionChanged(pCompressors, GetDlgItem(hwnd, IDC_AUDIOCOMPRESSORS));  
            pCompressors->Release(); 
         } 
         break;  
          
      case IDC_REFRESHVIDEOCOMPRESSORS:  
         // initialize the video compressor listbox 
         g_pCapture->get_VideoCompressors (&pCompressors);  
         RefreshCompressorList(pCompressors, GetDlgItem(hwnd, IDC_VIDEOCOMPRESSORS));  
         pCompressors->Release(); 
         return TRUE;  
         break;  
 
      case IDC_VIDEOCOMPRESSORS:  
         if (HIWORD(wParam) == LBN_SELCHANGE)  
         { 
            // select the video compressor 
            g_pCapture->get_VideoCompressors (&pCompressors);  
            CompressorSelectionChanged(pCompressors, GetDlgItem(hwnd, IDC_VIDEOCOMPRESSORS));  
            pCompressors->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_COMPRESSORDLG, NULL, CompressorDlgProc);  
 
 
error:  
   // cleanup 
 
   if (g_pCapture)  
      g_pCapture->Release(); 
 
   CoUninitialize(); 
    
   return 0;  
}