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 Source 

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

C++ Source 

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

  1. 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 Source 

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++ Source 

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

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

C Source 

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++ Source 

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);

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

C Source 

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++ Source 

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();

  1. To view the graph in DirectShow GraphEdit

C Source 

IltmmCapture_EditGraph(pCapture);

C++ Source 

pCapture->EditGraph();

  1. 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 Source 

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++ Source 

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();

  1. 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 Source 

// 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++ Source 

// 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.

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

C Source 

// start running 
 IltmmCapture_StartCapture(pCapture, ltmmCapture_Mode_VideoAndAudio);

C++ Source 

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

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