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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