Save the Captured Data As MPEG

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 video devices to be used as the capture source. The ltmmCapture object contains video device collection objects. The first video device can be selected for capture by calling the device collection's put_Selection function:

   C API

   IltmmDevices* pDevices; 
    // get an interface into video devices collection 
    IltmmCapture_get_VideoDevices(pCapture, &pDevices); 
    // select the first video device 
    IltmmDevices_put_Selection (pDevices, 0); 
    // release collection 
    IUnknown_Release(pDevices); 

   C++

   IltmmDevices* pDevices; 
    // get an interface into video devices collection 
    pCapture->get_VideoDevices(&pDevices); 
    // select device 
    pDevices->put_Selection(0); 
    // release collection 
    pDevices->Release(); 

3. Define the target or output file, as demonstrated with the following code:

   C API

   BSTR bstr;  
    // create a string containing the target file path 
    bstr = SysAllocString(L"c:\\target.mpg");  
    // assign the target file path to the capture object 
    IltmmCapture_put_TargetFile (pCapture, bstr);  
    // free the string 
    SysFreeString(bstr); 

   C++

   BSTR bstr;  
    // create a string containing the target file path 
    bstr = SysAllocString(L"c:\\target.mpg");  
    // assign the target file path to the capture object 
    pCapture->put_TargetFile (bstr);  
    // free the string 
    SysFreeString(bstr); 

4. Select the Video and Audio compressors, as demonstrated with the following code:

   C API

   long index; 
   IltmmCompressors* pCompressors; 
   // select the MS MPEG-4 Video Codec 
   IltmmCapture_get_VideoCompressors(pCapture, &pCompressors); 
   bstr = SysAllocString(L"@device:sw:{33D9A760-90C8-11D0-BD43-00A0C911CE86}\\Microsoft MPEG-4 Video Codec V2"); 
   IltmmCompressors_Find(pCompressors, bstr, &index); 
   SysFreeString(bstr); 
   if(index >= 0) 
      IltmmCompressors_put_Selection(pCompressors, index); 
   IUnknown_Release(pCompressors); 
   // select the MP3 audio video compressor 
   IltmmCapture_get_AudioCompressors(pCapture, &pCompressors); 
   bstr = SysAllocString(L"@device:cm:{33D9A761-90C8-11D0-BD43-00A0C911CE86}\\85MPEG Layer-3"); 
   IltmmCompressors_Find(pCompressors, bstr, &index); 
   SysFreeString(bstr); 
   if(index >= 0) 
      IltmmCompressors_put_Selection(pCompressors, index); 
   IUnknown_Release(pCompressors); 

   C++

   IltmmCompressors* pCompressors; 
   long index; 
   // select the MS MPEG-4 Video Codec 
   pCapture->get_VideoCompressors (&pCompressors); 
   bstr = SysAllocString(L"@device:sw:{33D9A760-90C8-11D0-BD43-00A0C911CE86}\\Microsoft MPEG-4 Video Codec V2"); 
   pCompressors->Find (bstr, &index); 
   SysFreeString(bstr); 
   if(index < 0) 
   { 
      // compressor isn't registered 
      pCompressors->Release (); 
      return E_FAIL; 
   } 
   pCompressors->put_Selection (index); 
   pCompressors->Release(); 
   // select the MP3 audio video compressor 
   pCapture->get_AudioCompressors (&pCompressors); 
   bstr = SysAllocString(L"@device:cm:{33D9A761-90C8-11D0-BD43-00A0C911CE86}\\85MPEG Layer-3"); 
   pCompressors->Find (bstr, &index); 
   SysFreeString(bstr); 
   if(index < 0) 
   { 
      // compressor isn't registered 
      pCompressors->Release (); 
      return E_FAIL; 
   } 
   pCompressors->put_Selection (index); 
   pCompressors->Release(); 

5. To view the graph in DirectShow GraphEdit

   C API

   IltmmCapture_EditGraph(pCapture); 

   C++

   pCapture->EditGraph(); 

6. Set the MPEG multiplexer. This example will use an AVI multiplexer because it is available on all computers. You should use a real MPEG multiplexer, as demonstrated with the following code:

   C API

   IltmmTargetFormats* pTargetFormats; 
   IltmmTargetFormat* pTargetFormat; 
   IltmmCapture_get_TargetFormats(pCapture, &pTargetFormats); 
   // retrieve collection item 
   IltmmTargetFormats_Item(pTargetFormats, 0, &pTargetFormat); 
   // assign the required Mux 
   // this case: AVI 
   bstr = SysAllocString(L"@device:sw:{083863F1-70DE-11D0-BD40-00A0C911CE86}\\{E2510970-F137-11CE-8B67-00AA00A3F1A6}"); 
   IltmmTargetFormat_put_Mux(pTargetFormat, bstr); 
   SysFreeString(bstr); 
   // assign the optional SinkSubType 
   // this case: MEDIASUBTYPE_Avi 
   bstr = SysAllocString(L"{E436EB88-524F-11CE-9F53-0020AF0BA770}"); 
   IltmmTargetFormat_put_SinkSubType(pTargetFormat, bstr); 
   SysFreeString(bstr); 
   // assign an optional Sink 
   // this case: default 
   bstr = SysAllocString(L""); 
   IltmmTargetFormat_put_Sink(pTargetFormat, bstr); 
   SysFreeString(bstr); 
   IUnknown_Release(pTargetFormat); 

   C++

   IltmmTargetFormats* pTargetFormats; 
   IltmmTargetFormat* pTargetFormat; 
   pCapture->get_TargetFormats(&pTargetFormats); 
   // retrieve collection item 
   pTargetFormats->Item(0, &pTargetFormat); 
   // assign the required Mux 
   // this case: AVI 
   bstr = SysAllocString(L"@device:sw:{083863F1-70DE-11D0-BD40-00A0C911CE86}\\{E2510970-F137-11CE-8B67-00AA00A3F1A6}"); 
   pTargetFormat->put_Mux(bstr); 
   SysFreeString(bstr); 
   // assign the optional SinkSubType 
   // this case: MEDIASUBTYPE_Avi 
   bstr = SysAllocString(L"{E436EB88-524F-11CE-9F53-0020AF0BA770}"); 
   pTargetFormat->put_SinkSubType(bstr); 
   SysFreeString(bstr); 
   // assign an optional Sink 
   // this case: default 
   bstr = SysAllocString(L""); 
   pTargetFormat->put_Sink(bstr); 
   SysFreeString(bstr); 
   pTargetFormat->Release(); 

7. Set a frame rate supported by MPEG. Look at the documentation for your MPEG multiplexer to see which frame rates it supports. Common frame rates are: 23.976, 24, 25, 29.97, 30fps, as demonstrated with the following code:

   C API

   // set rate to 30 fps 
    IltmmCapture_put_UseFrameRate(pCapture, VARIANT_TRUE); 
    IltmmCapture_put_FrameRate(pCapture, 30.0); 
    // you should check with their particular compressor which frame rates are supported.  

   C++

   // set rate to 30 fps 
    pCapture->put_UseFrameRate(VARIANT_TRUE); 
    pCapture->put_FrameRate(30.0); 
    // you should check with their particular compressor which frame rates are supported.  

8. Now start to capture the data and save it to the target file by calling the following function:

   C API

   // start running 
    IltmmCapture_StartCapture(pCapture, ltmmCapture_Mode_VideoAndAudio);   

   C++

   // start running 
    pCapture->StartCapture(ltmmCapture_Mode_VideoAndAudio);