Writing Windows Media Files for C

You do not need do use software certificates on computers with Windows Media 9 or later. For more information, please see Windows Media Support.

To write Windows Media files on computers without Windows Media 9 components, an application must provide a software certificate, also called a key, at run time. For details on obtaining the certificate, see the Windows Media Format SDK. An application provides its certificate to the ltmmCapture or ltmmConvert objects by calling the IltmmCapture::put_WMCertificate or IltmmConvert::put_WMCertificate object methods. The certificate is obtained by calling the Windows Media Format SDK method WMCreateCertificate. The method returns a pointer to the certificate that was created. To build an application, include Wmsdkidl.h for the prototype for WMCreateCertificate, and link to the Wmstub.lib that you received from Microsoft.

The following code example illustrates the basic steps in this process:

// define helper macros for using interfaces under C 
#ifndef COBJMACROS 
   #define COBJMACROS 
#endif 
 
// include the LEAD Multimedia TOOLKIT header 
#include "ltmm.h"  
 
// include the Windows Media SDK header 
#include "wmsdkidl.h"  
 
// EnableWindowsMedia 
// enables the convert object to write Windows Media file formats 
// Call this function before starting a conversion to Windows Media Formats, on systems without Windows Media 9 or later. 
HRESULT EnableWindowsMedia(IltmmConvert* pConvert) 
{ 
   HRESULT hr;  
   IUnknown* punkCert;  
 
   // create Windows Media Certificate 
   hr = WMCreateCertificate(&punkCert);  
   if(SUCCEEDED(hr))  
   { 
      // assign the certificate to the convert object 
      hr = IltmmConvert_put_WMCertificate(pConvert, punkCert);  
      IUnknown_Release(punkCert);  
   }    
   return hr;  
} 

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