Use ltmmCapture to Perform a Capture and Save It as a WMV File

1. Create an instance of the ltmmCapture class. This is accomplished using the Win32 CoCreateInstance function, as follows:

   C API

   IltmmCapture* pCapture; 
   CoCreateInstance(&CLSID_ltmmCapture, NULL, CLSCTX_INPROC_SERVER,&IID_IltmmCapture,(void**) &pCapture); 

   C++

   IltmmCapture* pCapture; 
   CoCreateInstance(&CLSID_ltmmCapture, NULL, CLSCTX_INPROC_SERVER,&IID_IltmmCapture, (void**) &pCapture); 

2. Define the notification window, which receives the capture status notifications:

   C API

   HWND hwndNotify; 
   #define WM_CAPTURENOTIFY (WM_USER + 1000) 
   IltmmCapture_SetNotifyWindow(pCapture, (long) hwndNotify, WM_CAPTURENOTIFY); 

   C++

   HWND hwndNotify; 
   #define WM_CAPTURENOTIFY (WM_USER + 1000) 
   pCapture->SetNotifyWindow((long) hwndNotify, WM_CAPTURENOTIFY); 

   The above code instructs the capture object to send WM_CAPTURENOTIFY messages to the window procedure of hwndNotify. The wParam parameter of the window message will contain the notification code.

   Note

   A capture can be accomplished without using a notification window, but the user would be required to poll the objects state to determine when the capture has finished.

3. Define a frame window for the video preview:

   C API

   HWND  hwndFrame; 
   IltmmCapture_put_VideoWindowFrame(pCapture, (long) hwndFrame); 

   C++

   HWND hwndFrame; 
   pCapture->put_VideoWindowFrame((long) hwndFrame); 

   The user is required to create the window that serves as the video frame. ltmmCapture will subclass this window, so there is no need to forward any messages to the ltmmCapture object. By default, ltmmCapture will automatically maximize the video within the frame window. The video will automatically resize when the frame window size changes.

   Note

   The notification window and the video frame window can be the same.

4. Set the Target file:

   C API

   BSTR bstr; 
   bstr = SysAllocString(L"c:\\captured.asf"); 
   IltmmCapture_put_TargetFile(pCapture, bstr); 
   SysFreeString(bstr); 

   C++

   BSTR bstr; 
   ::SysAllocString(L"c:\\captured.asf"); 
   pCapture->put_TargetFile(bstr); 
   ::SysFreeString(bstr); 

5. Set the video device:

   C API

   IltmmDevices* devices; 
   IltmmCapture_get_VideoDevices(pCapture, &devices); 
   IltmmDevices_put_Selection(devices, 0); 
   IltmmDevices_Release(devices); 

   C++

   IltmmDevices* devices; 
   pCapture->get_VideoDevices(&devices); 
   devices->put_Selection(0); 
   devices->Release(); 

6. Set the audio device:

   C API

   HIltmmDevices* devices; 
   IltmmCapture_get_AudioDevices(pCapture, &devices); 
   IltmmDevices_put_Selection(devices, 0); 
   IltmmDevices_Release(devices); 

   C++

   IltmmDevices* devices; 
   pCapture->get_AudioDevices(&devices); 
   devices->put_Selection(0); 
   devices->Release(); 

7. Set the target format:

   C API

   IltmmCapture_put_TargetFormat(pCapture, ltmmCapture_TargetFormat_Asf); 

   C++

   pCapture->put_TargetFormat(ltmmCapture_TargetFormat_Asf); 

8. When you want to start capturing, call the StartCapture function as follows:

   C API

   IltmmCapture_StartCapture(pCapture, ltmmCapture_Mode_VideoAndAudio) 

   C++

   pCapture->StartCapture(ltmmCapture_Mode_VideoAndAudio); 

9. When you want to stop capturing, call the StopCapture function as follows:

   C API

   IltmmCapture_StopCapture(pCapture); 

   C++

   pCapture->StopCapture(); 

10. Release the capture object (and all active objects) when you are done.