本文以一个Transform Filter为例，一步步整理Transform Filter一般开发步骤。
本文的Filter名为GrayFilter，把YUV视频信号转化为灰度信号，造成黑白电视的效果。
1. 配置开发环境
1. VC中在Tools->Options->Directories 设置好DirectX SDK的头文件和库文件路径
2. 编译了基类源码,生成strmbasd.lib (debug版), strmbase.lib(release版)
3. VC向导新建一个win32 DLL工程
4. Setting->Link->Output file name: GrayFilter.ax
5. Setting->Link加入strmbasd.lib winmm.lib quartz.lib vfw32.lib
6. 定义一个同名.def文件，加入到工程，内容如下：
LIBRARY GrayFilter.ax
EXPORTS
DllMain PRIVATE
DllGetClassObject PRIVATE
DllCanUnloadNow PRIVATE
DllRegisterServer PRIVATE
DllUnregisterServer PRIVATE
7. 定义DLL的入口函数及注册
extern "C" BOOL WINAPI DllEntryPoint(HINSTANCE, ULONG, LPVOID);BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved )
...{
return DllEntryPoint((HINSTANCE)(hModule), ul_reason_for_call, lpReserved);
}//// DllRegisterServer//// Handle registration of this filter//STDAPI DllRegisterServer()...{ return AMovieDllRegisterServer2(TRUE);} // DllRegisterServer//// DllUnregisterServer//STDAPI DllUnregisterServer()...{ return AMovieDllRegisterServer2(FALSE);} // DllUnregisterServer 8. 相关的头文件
#include <olectl.h>
#include <initguid.h>
#include <streams.h>
#if (1100 > _MSC_VER)
#include <olectlid.h>
#endif
#include <olectlid.h>
#endif
2. 开发Filter
1. 生成GUID( 命令行模式下运行guidgen工具)
// {C26EA242-43E4-4326-9304-1CB6ECD29B25}
DEFINE_GUID(CLSID_GrayFilter,
0xc26ea242, 0x43e4, 0x4326, 0x93, 0x4, 0x1c, 0xb6, 0xec, 0xd2, 0x9b, 0x25);
DEFINE_GUID(CLSID_GrayFilter,
0xc26ea242, 0x43e4, 0x4326, 0x93, 0x4, 0x1c, 0xb6, 0xec, 0xd2, 0x9b, 0x25);
2. 继承自Transform Filter
3. 按格式改写构造函数
CVideoGray(TCHAR *tszName, LPUNKNOWN pUnk, HRESULT *phr) :
CTransformFilter(NAME("Video to Gray"), pUnk, CLSID_GrayFilter)
{ }
CTransformFilter(NAME("Video to Gray"), pUnk, CLSID_GrayFilter)
{ }
4. 改写CTransformFilter几个重要函数
HRESULT CheckInputType(const CMediaType *mtIn);
HRESULT CheckTransform(const CMediaType *mtIn, const CMediaType *mtOut);
HRESULT DecideBufferSize(IMemAllocator *pAlloc,
ALLOCATOR_PROPERTIES *pProp);
HRESULT GetMediaType(int iPosition, CMediaType *pMediaType);
HRESULT Transform(IMediaSample *pIn, IMediaSample *pOut);
HRESULT CheckTransform(const CMediaType *mtIn, const CMediaType *mtOut);
HRESULT DecideBufferSize(IMemAllocator *pAlloc,
ALLOCATOR_PROPERTIES *pProp);
HRESULT GetMediaType(int iPosition, CMediaType *pMediaType);
HRESULT Transform(IMediaSample *pIn, IMediaSample *pOut);
5. 注册Filter信息
// 注册信息const AMOVIESETUP_MEDIATYPE sudPinTypes =...{ &MEDIATYPE_Video, // Major type &MEDIASUBTYPE_NULL // Minor type};const AMOVIESETUP_FILTER sudContrast =...{ &CLSID_GrayFilter, // Filter CLSID L"Video to Gray", // Filter name MERIT_DO_NOT_USE, // Its merit 0, // Number of pins NULL // Pin details};// List of class IDs and creator functions for the class factory. This// provides the link between the OLE entry point in the DLL and an object// being created. The class factory will call the static CreateInstanceCFactoryTemplate g_Templates[1] = ...{
...{ L"Video to Gray" , &CLSID_GrayFilter , CVideoGray::CreateInstance , NULL
, &sudContrast }};int g_cTemplates = sizeof(g_Templates) / sizeof(g_Templates[0]);
编译成功后生成GrayFilter.ax
命令行运行regsvr32 GrayFilter.ax注册即可