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Building DirectShow Filters

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[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The DirectShow base classes are recommended for implementing DirectShow filters. To build with the base classes, perform the following steps, in addition to the steps listed in Setting Up the Build Environment:

  • Build the base class library, located in the directory Samples\Multimedia\DirectShow\BaseClasses, under the SDK root directory. There are two versions of the library: a retail version (Strmbase.lib) and a debug version (Strmbasd.lib).
  • Include the header file Streams.h.
  • Use the __stdcall calling convention.
  • Use the multithreaded C run-time library (debug or retail, as appropriate).
  • Include a definition (.def) file that exports the DLL functions. The following is an example of a definition file. It assumes that the output file is named MyFilter.dll.
LIBRARY MYFILTER.DLL
EXPORTS 
    DllMain             PRIVATE
    DllGetClassObject   PRIVATE
    DllCanUnloadNow     PRIVATE
    DllRegisterServer   PRIVATE
    DllUnregisterServer PRIVATE
  • Link to the following lib files.
Label Value
Debug Build Strmbasd.lib, Msvcrtd.lib, Winmm.lib
Retail Build Strmbase.lib, Msvcrt.lib, Winmm.lib
  • Choose the "ignore default libraries" option in the linker settings.
  • Declare the DLL entry point in your source code, as follows:
extern "C" BOOL WINAPI DllEntryPoint(HINSTANCE, ULONG, LPVOID);
BOOL APIENTRY DllMain(HANDLE hModule, DWORD dwReason, LPVOID lpReserved)
{
    return DllEntryPoint((HINSTANCE)(hModule), dwReason, lpReserved);
}

Previous Versions

For versions of the base class library before DirectShow 9.0, you must also do the following:

  • For debug builds, define the preprocessor flag DEBUG.

This step is not required for the version of the base class library that is available in DirectShow 9.0 and later.

DirectShow Base Classes

Writing DirectShow Filters