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转载请标明是引用于 参考书<<DirectShow开发指南>>   DirectShow SDK提供了一套开发Filter的基类源代码。基于这些基类开发Filter将大大简化开发过程。 1、CBaseObject 大部分SDK类都从CBaseObject类(参见combase.h)中继承而来的。 class CBaseObject  {    private:        // Disable the copy constructor and assignment by default so you will get      //   compiler errors instead of unexpected behaviour if you pass objects      //   by value or assign objects.      CBaseObject(const CBaseObject& objectSrc);          // no implementation      void operator=(const CBaseObject& objectSrc);       // no implementation    private:      static LONG m_cObjects;     /* Total number of objects active */    protected:  #ifdef DEBUG      DWORD m_dwCookie;           /* Cookie identifying this object */  #endif      public:        /* These increment and decrement the number of active objects */        CBaseObject(const TCHAR *pName);  #ifdef UNICODE      CBaseObject(const char *pName);  #endif      ~CBaseObject();        /* Call this to find if there are any CUnknown derived objects active */        static LONG ObjectsActive() {          return m_cObjects;      };  };   class CBaseObject { private: // Disable the copy constructor and assignment by default so you will get // compiler errors instead of unexpected behaviour if you pass objects // by value or assign objects. CBaseObject(const CBaseObject& objectSrc); // no implementation void operator=(const CBaseObject& objectSrc); // no implementation private: static LONG m_cObjects; /* Total number of objects active */ protected: #ifdef DEBUG DWORD m_dwCookie; /* Cookie identifying this object */ #endif public: /* These increment and decrement the number of active objects */ CBaseObject(const TCHAR *pName); #ifdef UNICODE CBaseObject(const char *pName); #endif ~CBaseObject(); /* Call this to find if there are any CUnknown derived objects active */ static LONG ObjectsActive() { return m_cObjects; }; };   2、 CUnknown 作为COM组件(参见combase.cpp文件),最基本的当然是IUnknown接口的实现。SDK提供了CUnknown类,SDK实现了COM接口类都是直接或间接从这个类继承来的。 class AM_NOVTABLE CUnknown : public INonDelegatingUnknown,                   public CBaseObject  {  private:      const LPUNKNOWN m_pUnknown; /* Owner of this object */    protected:                      /* So we can override NonDelegatingRelease() */      volatile LONG m_cRef;       /* Number of reference counts */    public:        CUnknown(const TCHAR *pName, LPUNKNOWN pUnk);      virtual ~CUnknown() {};        // This is redundant, just use the other constructor      //   as we never touch the HRESULT in this anyway      CUnknown(TCHAR *pName, LPUNKNOWN pUnk,HRESULT *phr);  #ifdef UNICODE      CUnknown(const char *pName, LPUNKNOWN pUnk);      CUnknown(char *pName, LPUNKNOWN pUnk,HRESULT *phr);  #endif        /* Return the owner of this object */        LPUNKNOWN GetOwner() const {          return m_pUnknown;      };        /* Called from the class factory to create a new instance, it is        pure virtual so it must be overriden in your derived class */        /* static CUnknown *CreateInstance(LPUNKNOWN, HRESULT *) */        /* Non delegating unknown implementation */        STDMETHODIMP NonDelegatingQueryInterface(REFIID, void **);      STDMETHODIMP_(ULONG) NonDelegatingAddRef();      STDMETHODIMP_(ULONG) NonDelegatingRelease();  };   class AM_NOVTABLE CUnknown : public INonDelegatingUnknown, public CBaseObject { private: const LPUNKNOWN m_pUnknown; /* Owner of this object */ protected: /* So we can override NonDelegatingRelease() */ volatile LONG m_cRef; /* Number of reference counts */ public: CUnknown(const TCHAR *pName, LPUNKNOWN pUnk); virtual ~CUnknown() {}; // This is redundant, just use the other constructor // as we never touch the HRESULT in this anyway CUnknown(TCHAR *pName, LPUNKNOWN pUnk,HRESULT *phr); #ifdef UNICODE CUnknown(const char *pName, LPUNKNOWN pUnk); CUnknown(char *pName, LPUNKNOWN pUnk,HRESULT *phr); #endif /* Return the owner of this object */ LPUNKNOWN GetOwner() const { return m_pUnknown; }; /* Called from the class factory to create a new instance, it is pure virtual so it must be overriden in your derived class */ /* static CUnknown *CreateInstance(LPUNKNOWN, HRESULT *) */ /* Non delegating unknown implementation */ STDMETHODIMP NonDelegatingQueryInterface(REFIID, void **); STDMETHODIMP_(ULONG) NonDelegatingAddRef(); STDMETHODIMP_(ULONG) NonDelegatingRelease(); };   CUnknown类从CBaseObject中继承而来,另外CUnknown类还实现了INonDelegatingUnknown接口,用于支持引用计数、接口查询、COM组件“聚合”等。 CUnknown类的使用方法如下: (1) 从CUnknown派生一个子类,并在子类的public区加入DECLARE_IUNKNOWN宏; (2) 重写NonDelegatingQueryInterface函数,用以支持IUnknown外的其他接口; (3) 在子类的构造函数中调用CUnknown的构造函数。 eg: class CSeekingPassThru : public ISeekingPassThru, public CUnknown  {  public:      static CUnknown *CreateInstance(LPUNKNOWN pUnk, HRESULT *phr);      CSeekingPassThru(TCHAR *pName, LPUNKNOWN pUnk, HRESULT *phr);      ~CSeekingPassThru();        DECLARE_IUNKNOWN;      STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void ** ppv);        STDMETHODIMP Init(BOOL bSupportRendering, IPin *pPin);    private:      CPosPassThru              *m_pPosPassThru;  };   class CSeekingPassThru : public ISeekingPassThru, public CUnknown { public: static CUnknown *CreateInstance(LPUNKNOWN pUnk, HRESULT *phr); CSeekingPassThru(TCHAR *pName, LPUNKNOWN pUnk, HRESULT *phr); ~CSeekingPassThru(); DECLARE_IUNKNOWN; STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void ** ppv); STDMETHODIMP Init(BOOL bSupportRendering, IPin *pPin); private: CPosPassThru *m_pPosPassThru; };      CSeekingPassThru::CSeekingPassThru( TCHAR *pName, LPUNKNOWN pUnk, HRESULT *phr )                              : CUnknown(pName, pUnk, phr),                              m_pPosPassThru(NULL)  {  }   CSeekingPassThru::CSeekingPassThru( TCHAR *pName, LPUNKNOWN pUnk, HRESULT *phr ) : CUnknown(pName, pUnk, phr), m_pPosPassThru(NULL) { }   3、 CBaseFilter 最基本的Filter由CBaseFilter 类(参见amfilter.cpp)实现。 作为Filter的基本特征,CBaseFilter实现了IBaseFilter接口(IbaseFilter从IMediaFilter继承而来)。 同时CBaseFilter还实现了Filter框架(描述了各个Pin组件的情况)。 class AM_NOVTABLE CBaseFilter : public CUnknown,        // Handles an IUnknown                      public IBaseFilter,     // The Filter Interface                      public IAMovieSetup     // For un/registration  {    friend class CBasePin;    protected:      FILTER_STATE    m_State;            // current state: running, paused      IReferenceClock *m_pClock;          // this graph's ref clock      CRefTime        m_tStart;           // offset from stream time to reference time      CLSID       m_clsid;            // This filters clsid                                          // used for serialization      CCritSec        *m_pLock;           // Object we use for locking        WCHAR           *m_pName;           // Full filter name      IFilterGraph    *m_pGraph;          // Graph we belong to      IMediaEventSink *m_pSink;           // Called with notify events      LONG            m_PinVersion;       // Current pin version    public:        CBaseFilter(          const TCHAR *pName,     // Object description          LPUNKNOWN pUnk,         // IUnknown of delegating object          CCritSec  *pLock,       // Object who maintains lock      REFCLSID   clsid);      // The clsid to be used to serialize this filter        CBaseFilter(          TCHAR     *pName,       // Object description          LPUNKNOWN pUnk,         // IUnknown of delegating object          CCritSec  *pLock,       // Object who maintains lock      REFCLSID   clsid,       // The clsid to be used to serialize this filter          HRESULT   *phr);        // General OLE return code  #ifdef UNICODE      CBaseFilter(          const CHAR *pName,     // Object description          LPUNKNOWN pUnk,         // IUnknown of delegating object          CCritSec  *pLock,       // Object who maintains lock      REFCLSID   clsid);      // The clsid to be used to serialize this filter        CBaseFilter(          CHAR     *pName,       // Object description          LPUNKNOWN pUnk,         // IUnknown of delegating object          CCritSec  *pLock,       // Object who maintains lock      REFCLSID   clsid,       // The clsid to be used to serialize this filter          HRESULT   *phr);        // General OLE return code  #endif      ~CBaseFilter();        DECLARE_IUNKNOWN        // override this to say what interfaces we support where      STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void ** ppv);  #ifdef DEBUG      STDMETHODIMP_(ULONG) NonDelegatingRelease();  #endif        //      // --- IPersist method ---      //        STDMETHODIMP GetClassID(CLSID *pClsID);        // --- IMediaFilter methods ---        STDMETHODIMP GetState(DWORD dwMSecs, FILTER_STATE *State);        STDMETHODIMP SetSyncSource(IReferenceClock *pClock);        STDMETHODIMP GetSyncSource(IReferenceClock **pClock);          // override Stop and Pause so we can activate the pins.      // Note that Run will call Pause first if activation needed.      // Override these if you want to activate your filter rather than      // your pins.      STDMETHODIMP Stop();      STDMETHODIMP Pause();        // the start parameter is the difference to be added to the      // sample's stream time to get the reference time for      // its presentation      STDMETHODIMP Run(REFERENCE_TIME tStart);        // --- helper methods ---        // return the current stream time - ie find out what      // stream time should be appearing now      virtual HRESULT StreamTime(CRefTime& rtStream);        // Is the filter currently active?      BOOL IsActive() {          CAutoLock cObjectLock(m_pLock);          return ((m_State == State_Paused) || (m_State == State_Running));      };        // Is this filter stopped (without locking)      BOOL IsStopped() {          return (m_State == State_Stopped);      };        //      // --- IBaseFilter methods ---      //        // pin enumerator      STDMETHODIMP EnumPins(                      IEnumPins ** ppEnum);          // default behaviour of FindPin assumes pin ids are their names      STDMETHODIMP FindPin(          LPCWSTR Id,          IPin ** ppPin      );        STDMETHODIMP QueryFilterInfo(                      FILTER_INFO * pInfo);        STDMETHODIMP JoinFilterGraph(                      IFilterGraph * pGraph,                      LPCWSTR pName);        // return a Vendor information string. Optional - may return E_NOTIMPL.      // memory returned should be freed using CoTaskMemFree      // default implementation returns E_NOTIMPL      STDMETHODIMP QueryVendorInfo(                      LPWSTR* pVendorInfo              );        // --- helper methods ---        // send an event notification to the filter graph if we know about it.      // returns S_OK if delivered, S_FALSE if the filter graph does not sink      // events, or an error otherwise.      HRESULT NotifyEvent(          long EventCode,          LONG_PTR EventParam1,          LONG_PTR EventParam2);        // return the filter graph we belong to      IFilterGraph *GetFilterGraph() {          return m_pGraph;      }        // Request reconnect      // pPin is the pin to reconnect      // pmt is the type to reconnect with - can be NULL      // Calls ReconnectEx on the filter graph      HRESULT ReconnectPin(IPin *pPin, AM_MEDIA_TYPE const *pmt);        // find out the current pin version (used by enumerators)      virtual LONG GetPinVersion();      void IncrementPinVersion();        // you need to supply these to access the pins from the enumerator      // and for default Stop and Pause/Run activation.      virtual int GetPinCount() PURE;      virtual CBasePin *GetPin(int n) PURE;        // --- IAMovieSetup methods ---        STDMETHODIMP Register();    // ask filter to register itself      STDMETHODIMP Unregister();  // and unregister itself        // --- setup helper methods ---      // (override to return filters setup data)        virtual LPAMOVIESETUP_FILTER GetSetupData(){ return NULL; }    };   class AM_NOVTABLE CBaseFilter : public CUnknown, // Handles an IUnknown public IBaseFilter, // The Filter Interface public IAMovieSetup // For un/registration { friend class CBasePin; protected: FILTER_STATE m_State; // current state: running, paused IReferenceClock *m_pClock; // this graph's ref clock CRefTime m_tStart; // offset from stream time to reference time CLSID m_clsid; // This filters clsid // used for serialization CCritSec *m_pLock; // Object we use for locking WCHAR *m_pName; // Full filter name IFilterGraph *m_pGraph; // Graph we belong to IMediaEventSink *m_pSink; // Called with notify events LONG m_PinVersion; // Current pin version public: CBaseFilter( const TCHAR *pName, // Object description LPUNKNOWN pUnk, // IUnknown of delegating object CCritSec *pLock, // Object who maintains lock REFCLSID clsid); // The clsid to be used to serialize this filter CBaseFilter( TCHAR *pName, // Object description LPUNKNOWN pUnk, // IUnknown of delegating object CCritSec *pLock, // Object who maintains lock REFCLSID clsid, // The clsid to be used to serialize this filter HRESULT *phr); // General OLE return code #ifdef UNICODE CBaseFilter( const CHAR *pName, // Object description LPUNKNOWN pUnk, // IUnknown of delegating object CCritSec *pLock, // Object who maintains lock REFCLSID clsid); // The clsid to be used to serialize this filter CBaseFilter( CHAR *pName, // Object description LPUNKNOWN pUnk, // IUnknown of delegating object CCritSec *pLock, // Object who maintains lock REFCLSID clsid, // The clsid to be used to serialize this filter HRESULT *phr); // General OLE return code #endif ~CBaseFilter(); DECLARE_IUNKNOWN // override this to say what interfaces we support where STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void ** ppv); #ifdef DEBUG STDMETHODIMP_(ULONG) NonDelegatingRelease(); #endif // // --- IPersist method --- // STDMETHODIMP GetClassID(CLSID *pClsID); // --- IMediaFilter methods --- STDMETHODIMP GetState(DWORD dwMSecs, FILTER_STATE *State); STDMETHODIMP SetSyncSource(IReferenceClock *pClock); STDMETHODIMP GetSyncSource(IReferenceClock **pClock); // override Stop and Pause so we can activate the pins. // Note that Run will call Pause first if activation needed. // Override these if you want to activate your filter rather than // your pins. STDMETHODIMP Stop(); STDMETHODIMP Pause(); // the start parameter is the difference to be added to the // sample's stream time to get the reference time for // its presentation STDMETHODIMP Run(REFERENCE_TIME tStart); // --- helper methods --- // return the current stream time - ie find out what // stream time should be appearing now virtual HRESULT StreamTime(CRefTime& rtStream); // Is the filter currently active? BOOL IsActive() { CAutoLock cObjectLock(m_pLock); return ((m_State == State_Paused) || (m_State == State_Running)); }; // Is this filter stopped (without locking) BOOL IsStopped() { return (m_State == State_Stopped); }; // // --- IBaseFilter methods --- // // pin enumerator STDMETHODIMP EnumPins( IEnumPins ** ppEnum); // default behaviour of FindPin assumes pin ids are their names STDMETHODIMP FindPin( LPCWSTR Id, IPin ** ppPin ); STDMETHODIMP QueryFilterInfo( FILTER_INFO * pInfo); STDMETHODIMP JoinFilterGraph( IFilterGraph * pGraph, LPCWSTR pName); // return a Vendor information string. Optional - may return E_NOTIMPL. // memory returned should be freed using CoTaskMemFree // default implementation returns E_NOTIMPL STDMETHODIMP QueryVendorInfo( LPWSTR* pVendorInfo ); // --- helper methods --- // send an event notification to the filter graph if we know about it. // returns S_OK if delivered, S_FALSE if the filter graph does not sink // events, or an error otherwise. HRESULT NotifyEvent( long EventCode, LONG_PTR EventParam1, LONG_PTR EventParam2); // return the filter graph we belong to IFilterGraph *GetFilterGraph() { return m_pGraph; } // Request reconnect // pPin is the pin to reconnect // pmt is the type to reconnect with - can be NULL // Calls ReconnectEx on the filter graph HRESULT ReconnectPin(IPin *pPin, AM_MEDIA_TYPE const *pmt); // find out the current pin version (used by enumerators) virtual LONG GetPinVersion(); void IncrementPinVersion(); // you need to supply these to access the pins from the enumerator // and for default Stop and Pause/Run activation. virtual int GetPinCount() PURE; virtual CBasePin *GetPin(int n) PURE; // --- IAMovieSetup methods --- STDMETHODIMP Register(); // ask filter to register itself STDMETHODIMP Unregister(); // and unregister itself // --- setup helper methods --- // (override to return filters setup data) virtual LPAMOVIESETUP_FILTER GetSetupData(){ return NULL; } };   CBaseFilter类的使用方法如下: (1) 声明一个新类是从CBaseFilter中继承而来; (2) 在新类中定义Filter上的Pin的实例(Pin从CBasePin类继承而来); (3) 实现纯虚函数CBaseFilter::GetPin,用于返回Filter上各个Pin的对象指针; (4) 实现纯虚函数CBaseFilter::GetPinCount,用于返回Filter上Pin 的数量; (5) 考虑如何处理从输入Pin进来的Sample数据。 eg: //  // The filter object itself. Supports IBaseFilter through  // CBaseFilter and also IFileSourceFilter directly in this object  // CAsyncReader类实现了一个Filter,它从CBaseFilter派生,实现了仅含一个输出  // Pin(CAsyncOutputPin类的实例)的Source filter框架。  class CAsyncReader : public CBaseFilter  {    protected:      // filter-wide lock      CCritSec m_csFilter;        // all i/o done here      CAsyncIo m_Io;        // (2)在新类中定义Filter上的Pin的实例(Pin从CBasePin类继承而来);      // our output pin      CAsyncOutputPin m_OutputPin;        // Type we think our data is      CMediaType m_mt;    public:                // construction / destruction        CAsyncReader(          TCHAR *pName,          LPUNKNOWN pUnk,          CAsyncStream *pStream, // 它是Filter获取数据的源          HRESULT *phr);        ~CAsyncReader();          //(3) 实现纯虚函数CBaseFilter::GetPin,用于返回Filter上各个Pin的对象指针;      //(4) 实现纯虚函数CBaseFilter::GetPinCount,用于返回Filter上Pin 的数量;      int GetPinCount();      CBasePin *GetPin(int n);        // --- Access our media type      const CMediaType *LoadType() const      {          return &m_mt;      }        virtual HRESULT Connect(          IPin * pReceivePin,          const AM_MEDIA_TYPE *pmt   // optional media type      )      {          return m_OutputPin.CBasePin::Connect(pReceivePin, pmt);      }  };   // // The filter object itself. Supports IBaseFilter through // CBaseFilter and also IFileSourceFilter directly in this object // CAsyncReader类实现了一个Filter,它从CBaseFilter派生,实现了仅含一个输出 // Pin(CAsyncOutputPin类的实例)的Source filter框架。 class CAsyncReader : public CBaseFilter { protected: // filter-wide lock CCritSec m_csFilter; // all i/o done here CAsyncIo m_Io; // (2)在新类中定义Filter上的Pin的实例(Pin从CBasePin类继承而来); // our output pin CAsyncOutputPin m_OutputPin; // Type we think our data is CMediaType m_mt; public: // construction / destruction CAsyncReader( TCHAR *pName, LPUNKNOWN pUnk, CAsyncStream *pStream, // 它是Filter获取数据的源 HRESULT *phr); ~CAsyncReader(); //(3) 实现纯虚函数CBaseFilter::GetPin,用于返回Filter上各个Pin的对象指针; //(4) 实现纯虚函数CBaseFilter::GetPinCount,用于返回Filter上Pin 的数量; int GetPinCount(); CBasePin *GetPin(int n); // --- Access our media type const CMediaType *LoadType() const { return &m_mt; } virtual HRESULT Connect( IPin * pReceivePin, const AM_MEDIA_TYPE *pmt // optional media type ) { return m_OutputPin.CBasePin::Connect(pReceivePin, pmt); } };   还有SDK类的CSource、CBaseRenderer、 CTracsformFilter都是从CBaseFilter继承来的,实现开发Filter时, 使用这些子类作为Filter类。 4、CBasePin Filter  上最基本的Pin由CBasePin类(参见 amfilter.h)实现。 作为Pin的基本特征,CBasePin实现了IPin接口。CBasePin设计了Pin 的整个连接过程。 另外,这个类还实现了IQualityControl接口,该接口用于质量控制。 class  AM_NOVTABLE CBasePin : public CUnknown, public IPin, public IQualityControl  {    protected:        WCHAR *         m_pName;                // This pin's name      IPin            *m_Connected;               // Pin we have connected to      PIN_DIRECTION   m_dir;                      // Direction of this pin      CCritSec        *m_pLock;                   // Object we use for locking      bool            m_bRunTimeError;            // Run time error generated      bool            m_bCanReconnectWhenActive;  // OK to reconnect when active      bool            m_bTryMyTypesFirst;         // When connecting enumerate                                                  // this pin's types first      CBaseFilter    *m_pFilter;                  // Filter we were created by      IQualityControl *m_pQSink;                  // Target for Quality messages      LONG            m_TypeVersion;              // Holds current type version      CMediaType      m_mt;                       // Media type of connection        CRefTime        m_tStart;                   // time from NewSegment call      CRefTime        m_tStop;                    // time from NewSegment      double          m_dRate;                    // rate from NewSegment    #ifdef DEBUG      LONG            m_cRef;                     // Ref count tracing  #endif        // displays pin connection information    #ifdef DEBUG      void DisplayPinInfo(IPin *pReceivePin);      void DisplayTypeInfo(IPin *pPin, const CMediaType *pmt);  #else      void DisplayPinInfo(IPin *pReceivePin) {};      void DisplayTypeInfo(IPin *pPin, const CMediaType *pmt) {};  #endif        // used to agree a media type for a pin connection        // given a specific media type, attempt a connection (includes      // checking that the type is acceptable to this pin)      HRESULT      AttemptConnection(          IPin* pReceivePin,      // connect to this pin          const CMediaType* pmt   // using this type      );        // try all the media types in this enumerator - for each that      // we accept, try to connect using ReceiveConnection.      HRESULT TryMediaTypes(                          IPin *pReceivePin,      // connect to this pin                          const CMediaType *pmt,        // proposed type from Connect                          IEnumMediaTypes *pEnum);    // try this enumerator        // establish a connection with a suitable mediatype. Needs to      // propose a media type if the pmt pointer is null or partially      // specified - use TryMediaTypes on both our and then the other pin's      // enumerator until we find one that works.      HRESULT AgreeMediaType(                          IPin *pReceivePin,      // connect to this pin                          const CMediaType *pmt);       // proposed type from Connect    public:        CBasePin(          TCHAR *pObjectName,         // Object description          CBaseFilter *pFilter,       // Owning filter who knows about pins          CCritSec *pLock,            // Object who implements the lock          HRESULT *phr,               // General OLE return code          LPCWSTR pName,              // Pin name for us          PIN_DIRECTION dir);         // Either PINDIR_INPUT or PINDIR_OUTPUT  #ifdef UNICODE      CBasePin(          CHAR *pObjectName,         // Object description          CBaseFilter *pFilter,       // Owning filter who knows about pins          CCritSec *pLock,            // Object who implements the lock          HRESULT *phr,               // General OLE return code          LPCWSTR pName,              // Pin name for us          PIN_DIRECTION dir);         // Either PINDIR_INPUT or PINDIR_OUTPUT  #endif      virtual ~CBasePin();        DECLARE_IUNKNOWN        STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void ** ppv);      STDMETHODIMP_(ULONG) NonDelegatingRelease();      STDMETHODIMP_(ULONG) NonDelegatingAddRef();        // --- IPin methods ---        // take lead role in establishing a connection. Media type pointer      // may be null, or may point to partially-specified mediatype      // (subtype or format type may be GUID_NULL).      STDMETHODIMP Connect(          IPin * pReceivePin,          const AM_MEDIA_TYPE *pmt   // optional media type      );        // (passive) accept a connection from another pin      STDMETHODIMP ReceiveConnection(          IPin * pConnector,      // this is the initiating connecting pin          const AM_MEDIA_TYPE *pmt   // this is the media type we will exchange      );        STDMETHODIMP Disconnect();        STDMETHODIMP ConnectedTo(IPin **pPin);        STDMETHODIMP ConnectionMediaType(AM_MEDIA_TYPE *pmt);        STDMETHODIMP QueryPinInfo(          PIN_INFO * pInfo      );        STDMETHODIMP QueryDirection(          PIN_DIRECTION * pPinDir      );        STDMETHODIMP QueryId(          LPWSTR * Id      );        // does the pin support this media type      STDMETHODIMP QueryAccept(          const AM_MEDIA_TYPE *pmt      );        // return an enumerator for this pins preferred media types      STDMETHODIMP EnumMediaTypes(          IEnumMediaTypes **ppEnum      );        // return an array of IPin* - the pins that this pin internally connects to      // All pins put in the array must be AddReffed (but no others)      // Errors: "Can't say" - FAIL, not enough slots - return S_FALSE      // Default: return E_NOTIMPL      // The filter graph will interpret NOT_IMPL as any input pin connects to      // all visible output pins and vice versa.      // apPin can be NULL if nPin==0 (not otherwise).      STDMETHODIMP QueryInternalConnections(          IPin* *apPin,     // array of IPin*          ULONG *nPin       // on input, the number of slots                            // on output  the number of pins      ) { return E_NOTIMPL; }        // Called when no more data will be sent      STDMETHODIMP EndOfStream(void);        // Begin/EndFlush still PURE        // NewSegment notifies of the start/stop/rate applying to the data      // about to be received. Default implementation records data and      // returns S_OK.      // Override this to pass downstream.      STDMETHODIMP NewSegment(                      REFERENCE_TIME tStart,                      REFERENCE_TIME tStop,                      double dRate);        //================================================================================      // IQualityControl methods      //================================================================================        STDMETHODIMP Notify(IBaseFilter * pSender, Quality q);        STDMETHODIMP SetSink(IQualityControl * piqc);        // --- helper methods ---        // Returns true if the pin is connected. false otherwise.      BOOL IsConnected(void) {return (m_Connected != NULL); };      // Return the pin this is connected to (if any)      IPin * GetConnected() { return m_Connected; };        // Check if our filter is currently stopped      BOOL IsStopped() {          return (m_pFilter->m_State == State_Stopped);      };        // find out the current type version (used by enumerators)      virtual LONG GetMediaTypeVersion();      void IncrementTypeVersion();        // switch the pin to active (paused or running) mode      // not an error to call this if already active      virtual HRESULT Active(void);        // switch the pin to inactive state - may already be inactive      virtual HRESULT Inactive(void);        // Notify of Run() from filter      virtual HRESULT Run(REFERENCE_TIME tStart);        // check if the pin can support this specific proposed type and format      virtual HRESULT CheckMediaType(const CMediaType *) PURE;        // set the connection to use this format (previously agreed)      virtual HRESULT SetMediaType(const CMediaType *);        // check that the connection is ok before verifying it      // can be overridden eg to check what interfaces will be supported.      virtual HRESULT CheckConnect(IPin *);        // Set and release resources required for a connection      virtual HRESULT BreakConnect();      virtual HRESULT CompleteConnect(IPin *pReceivePin);        // returns the preferred formats for a pin      virtual HRESULT GetMediaType(int iPosition,CMediaType *pMediaType);        // access to NewSegment values      REFERENCE_TIME CurrentStopTime() {          return m_tStop;      }      REFERENCE_TIME CurrentStartTime() {          return m_tStart;      }      double CurrentRate() {          return m_dRate;      }        //  Access name      LPWSTR Name() { return m_pName; };        //  Can reconnectwhen active?      void SetReconnectWhenActive(bool bCanReconnect)      {          m_bCanReconnectWhenActive = bCanReconnect;      }        bool CanReconnectWhenActive()      {          return m_bCanReconnectWhenActive;      }    protected:      STDMETHODIMP DisconnectInternal();  };   class AM_NOVTABLE CBasePin : public CUnknown, public IPin, public IQualityControl { protected: WCHAR * m_pName; // This pin's name IPin *m_Connected; // Pin we have connected to PIN_DIRECTION m_dir; // Direction of this pin CCritSec *m_pLock; // Object we use for locking bool m_bRunTimeError; // Run time error generated bool m_bCanReconnectWhenActive; // OK to reconnect when active bool m_bTryMyTypesFirst; // When connecting enumerate // this pin's types first CBaseFilter *m_pFilter; // Filter we were created by IQualityControl *m_pQSink; // Target for Quality messages LONG m_TypeVersion; // Holds current type version CMediaType m_mt; // Media type of connection CRefTime m_tStart; // time from NewSegment call CRefTime m_tStop; // time from NewSegment double m_dRate; // rate from NewSegment #ifdef DEBUG LONG m_cRef; // Ref count tracing #endif // displays pin connection information #ifdef DEBUG void DisplayPinInfo(IPin *pReceivePin); void DisplayTypeInfo(IPin *pPin, const CMediaType *pmt); #else void DisplayPinInfo(IPin *pReceivePin) {}; void DisplayTypeInfo(IPin *pPin, const CMediaType *pmt) {}; #endif // used to agree a media type for a pin connection // given a specific media type, attempt a connection (includes // checking that the type is acceptable to this pin) HRESULT AttemptConnection( IPin* pReceivePin, // connect to this pin const CMediaType* pmt // using this type ); // try all the media types in this enumerator - for each that // we accept, try to connect using ReceiveConnection. HRESULT TryMediaTypes( IPin *pReceivePin, // connect to this pin const CMediaType *pmt, // proposed type from Connect IEnumMediaTypes *pEnum); // try this enumerator // establish a connection with a suitable mediatype. Needs to // propose a media type if the pmt pointer is null or partially // specified - use TryMediaTypes on both our and then the other pin's // enumerator until we find one that works. HRESULT AgreeMediaType( IPin *pReceivePin, // connect to this pin const CMediaType *pmt); // proposed type from Connect public: CBasePin( TCHAR *pObjectName, // Object description CBaseFilter *pFilter, // Owning filter who knows about pins CCritSec *pLock, // Object who implements the lock HRESULT *phr, // General OLE return code LPCWSTR pName, // Pin name for us PIN_DIRECTION dir); // Either PINDIR_INPUT or PINDIR_OUTPUT #ifdef UNICODE CBasePin( CHAR *pObjectName, // Object description CBaseFilter *pFilter, // Owning filter who knows about pins CCritSec *pLock, // Object who implements the lock HRESULT *phr, // General OLE return code LPCWSTR pName, // Pin name for us PIN_DIRECTION dir); // Either PINDIR_INPUT or PINDIR_OUTPUT #endif virtual ~CBasePin(); DECLARE_IUNKNOWN STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void ** ppv); STDMETHODIMP_(ULONG) NonDelegatingRelease(); STDMETHODIMP_(ULONG) NonDelegatingAddRef(); // --- IPin methods --- // take lead role in establishing a connection. Media type pointer // may be null, or may point to partially-specified mediatype // (subtype or format type may be GUID_NULL). STDMETHODIMP Connect( IPin * pReceivePin, const AM_MEDIA_TYPE *pmt // optional media type ); // (passive) accept a connection from another pin STDMETHODIMP ReceiveConnection( IPin * pConnector, // this is the initiating connecting pin const AM_MEDIA_TYPE *pmt // this is the media type we will exchange ); STDMETHODIMP Disconnect(); STDMETHODIMP ConnectedTo(IPin **pPin); STDMETHODIMP ConnectionMediaType(AM_MEDIA_TYPE *pmt); STDMETHODIMP QueryPinInfo( PIN_INFO * pInfo ); STDMETHODIMP QueryDirection( PIN_DIRECTION * pPinDir ); STDMETHODIMP QueryId( LPWSTR * Id ); // does the pin support this media type STDMETHODIMP QueryAccept( const AM_MEDIA_TYPE *pmt ); // return an enumerator for this pins preferred media types STDMETHODIMP EnumMediaTypes( IEnumMediaTypes **ppEnum ); // return an array of IPin* - the pins that this pin internally connects to // All pins put in the array must be AddReffed (but no others) // Errors: "Can't say" - FAIL, not enough slots - return S_FALSE // Default: return E_NOTIMPL // The filter graph will interpret NOT_IMPL as any input pin connects to // all visible output pins and vice versa. // apPin can be NULL if nPin==0 (not otherwise). STDMETHODIMP QueryInternalConnections( IPin* *apPin, // array of IPin* ULONG *nPin // on input, the number of slots // on output the number of pins ) { return E_NOTIMPL; } // Called when no more data will be sent STDMETHODIMP EndOfStream(void); // Begin/EndFlush still PURE // NewSegment notifies of the start/stop/rate applying to the data // about to be received. Default implementation records data and // returns S_OK. // Override this to pass downstream. STDMETHODIMP NewSegment( REFERENCE_TIME tStart, REFERENCE_TIME tStop, double dRate); //================================================================================ // IQualityControl methods //================================================================================ STDMETHODIMP Notify(IBaseFilter * pSender, Quality q); STDMETHODIMP SetSink(IQualityControl * piqc); // --- helper methods --- // Returns true if the pin is connected. false otherwise. BOOL IsConnected(void) {return (m_Connected != NULL); }; // Return the pin this is connected to (if any) IPin * GetConnected() { return m_Connected; }; // Check if our filter is currently stopped BOOL IsStopped() { return (m_pFilter->m_State == State_Stopped); }; // find out the current type version (used by enumerators) virtual LONG GetMediaTypeVersion(); void IncrementTypeVersion(); // switch the pin to active (paused or running) mode // not an error to call this if already active virtual HRESULT Active(void); // switch the pin to inactive state - may already be inactive virtual HRESULT Inactive(void); // Notify of Run() from filter virtual HRESULT Run(REFERENCE_TIME tStart); // check if the pin can support this specific proposed type and format virtual HRESULT CheckMediaType(const CMediaType *) PURE; // set the connection to use this format (previously agreed) virtual HRESULT SetMediaType(const CMediaType *); // check that the connection is ok before verifying it // can be overridden eg to check what interfaces will be supported. virtual HRESULT CheckConnect(IPin *); // Set and release resources required for a connection virtual HRESULT BreakConnect(); virtual HRESULT CompleteConnect(IPin *pReceivePin); // returns the preferred formats for a pin virtual HRESULT GetMediaType(int iPosition,CMediaType *pMediaType); // access to NewSegment values REFERENCE_TIME CurrentStopTime() { return m_tStop; } REFERENCE_TIME CurrentStartTime() { return m_tStart; } double CurrentRate() { return m_dRate; } // Access name LPWSTR Name() { return m_pName; }; // Can reconnectwhen active? void SetReconnectWhenActive(bool bCanReconnect) { m_bCanReconnectWhenActive = bCanReconnect; } bool CanReconnectWhenActive() { return m_bCanReconnectWhenActive; } protected: STDMETHODIMP DisconnectInternal(); };   在CBasePin实现的成员函数中,有3个与Filter的状态转换相对应。 // 转换pin到活动状态(暂停或运行)    // not an error to call this if already active    virtual HRESULT Active(void);      // 转换pin到不活动状态 - 可能已经处于非活动状态    virtual HRESULT Inactive(void);      // 通知运行filter 的 Run()    virtual HRESULT Run(REFERENCE_TIME tStart);   // 转换pin到活动状态(暂停或运行) // not an error to call this if already active virtual HRESULT Active(void); // 转换pin到不活动状态 - 可能已经处于非活动状态 virtual HRESULT Inactive(void); // 通知运行filter 的 Run() virtual HRESULT Run(REFERENCE_TIME tStart);     我们来看一下Filter的Stop的实现,实际上就是调用Filter的所有pin的Inactive函数 STDMETHODIMP  CBaseFilter::Stop()  {      CAutoLock cObjectLock(m_pLock);      HRESULT hr = NOERROR;        // 通知所有pin改变状态      if (m_State != State_Stopped) {          int cPins = GetPinCount();          for (int c = 0; c < cPins; c++) {                CBasePin *pPin = GetPin(c);                // Disconnected pins are not activated - this saves pins worrying              // about this state themselves. We ignore the return code to make              // sure everyone is inactivated regardless. The base input pin              // class can return an error if it has no allocator but Stop can              // be used to resync the graph state after something has gone bad              // 仅在完成连接的pin上调用Inactive函数              // 如果Inactive函数返回一个错误值,则暂时忽略,              // 以便所有Pin都有机会被调用Inactive              if (pPin->IsConnected()) {                  HRESULT hrTmp = pPin->Inactive();                  if (FAILED(hrTmp) && SUCCEEDED(hr)) {                      hr = hrTmp;                  }              }          }      }          m_State = State_Stopped;      return hr;  }   STDMETHODIMP CBaseFilter::Stop() { CAutoLock cObjectLock(m_pLock); HRESULT hr = NOERROR; // 通知所有pin改变状态 if (m_State != State_Stopped) { int cPins = GetPinCount(); for (int c = 0; c < cPins; c++) { CBasePin *pPin = GetPin(c); // Disconnected pins are not activated - this saves pins worrying // about this state themselves. We ignore the return code to make // sure everyone is inactivated regardless. The base input pin // class can return an error if it has no allocator but Stop can // be used to resync the graph state after something has gone bad // 仅在完成连接的pin上调用Inactive函数 // 如果Inactive函数返回一个错误值,则暂时忽略, // 以便所有Pin都有机会被调用Inactive if (pPin->IsConnected()) { HRESULT hrTmp = pPin->Inactive(); if (FAILED(hrTmp) && SUCCEEDED(hr)) { hr = hrTmp; } } } } m_State = State_Stopped; return hr; }     在实际开发Filter的过程中,很有可能重写CBasePin::Inactive、 CBasePin::Active和CBasePin::Run这3个函数,以进行必要的初始化、释放资源等。 CBasePin类的使用方法如下: (1) 从CBasePin派生一个子类; (2) 实现纯虚函数CBasePIn::CheckMediaType,进行Pin连接时的媒体类型检查; (3) 实现纯虚函数CBasePin::GetMediaType,提供Pin上的首选媒体类型。 (4) 实现IPin::BeginFlush和IPin::EndFlush两个函数。 (5) 可能需要重写的函数包括 CBasePin::Active()  实现资源分配 CBasePin::Inactive  实现资源释放 CBasePin::Run  在Filter运行前进行一些初始化 CBasePin::CheckConnect  连接时检查,如查询对方Pin上是否支持某个特殊接口 CBasePin::BreakConnect 断开连接,并进行必要的资源释放 CBasePin::CompleteConnect  完成连接时被调用,可以在这个函数中获得当前连接的媒体类型参数 CBasePin::EndOfStream 当上流数据全部传送完毕后被调用。                     如果这个是Transform Filter,则将EndOfStream继续入下传送;                    如果是Renderer Filter,需要向Filter Graph Manager发送一个EC_COMPLETE事件 CBasePin::Noftify  直接响应质量控制。 eg: // CAsyncOutputPin实现了一个输出Pin  // 继承自IAsyncReader、CBasePin,这是对拉模式的Source Filter的基本要求  /* IAsyncReader接口方法及描述如下: BeginFlush  放弃所有正在进行的数据读取 EndFlush    与BeginFlush配对,标示Flush过程结束 Length      得到数据总长度和当前可以读取的长度 RequestAlloctor 要求一个输入Pin上的Sample管理器 Request     发出一个数据请求 SyncReadAligned 同步读取数据(边界对齐) SyncRead    同步读取数据 WaitForNext 等待一个请求的完成 ====================================================================== 可以看出CAsyOutputPin类上实现的IAsyncReader的各个接口方法,都“委托” 给了CAsyncIo类对象的同名成员函数 */  class CAsyncOutputPin    : public IAsyncReader,       public CBasePin  {  protected:      CAsyncReader* m_pReader;      CAsyncIo * m_pIo;        //  This is set every time we're asked to return an IAsyncReader      //  interface      //  This allows us to know if the downstream pin can use      //  this transport, otherwise we can hook up to thinks like the      //  dump filter and nothing happens      BOOL         m_bQueriedForAsyncReader;        HRESULT InitAllocator(IMemAllocator **ppAlloc);    public:      // constructor and destructor      CAsyncOutputPin(          HRESULT * phr,          CAsyncReader *pReader,          CAsyncIo *pIo,          CCritSec * pLock);        ~CAsyncOutputPin();        // --- CUnknown ---        // need to expose IAsyncReader      DECLARE_IUNKNOWN      STDMETHODIMP NonDelegatingQueryInterface(REFIID, void**);        // --- IPin methods ---      STDMETHODIMP Connect(          IPin * pReceivePin,          const AM_MEDIA_TYPE *pmt   // optional media type      );        // --- CBasePin methods ---        // return the types we prefer - this will return the known      // file type      HRESULT GetMediaType(int iPosition, CMediaType *pMediaType);        // can we support this type?      HRESULT CheckMediaType(const CMediaType* pType);        // Clear the flag so we see if IAsyncReader is queried for      HRESULT CheckConnect(IPin *pPin)      {          m_bQueriedForAsyncReader = FALSE;          return CBasePin::CheckConnect(pPin);      }        // See if it was asked for      HRESULT CompleteConnect(IPin *pReceivePin)      {          if (m_bQueriedForAsyncReader) {              return CBasePin::CompleteConnect(pReceivePin);          } else {    #ifdef VFW_E_NO_TRANSPORT              return VFW_E_NO_TRANSPORT;  #else              return E_FAIL;  #endif          }      }        //  Remove our connection status      HRESULT BreakConnect()      {          m_bQueriedForAsyncReader = FALSE;          return CBasePin::BreakConnect();      }        // --- IAsyncReader methods ---      // pass in your preferred allocator and your preferred properties.      // method returns the actual allocator to be used. Call GetProperties      // on returned allocator to learn alignment and prefix etc chosen.      // this allocator will be not be committed and decommitted by      // the async reader, only by the consumer.      STDMETHODIMP RequestAllocator(                        IMemAllocator* pPreferred,                        ALLOCATOR_PROPERTIES* pProps,                        IMemAllocator ** ppActual);        // queue a request for data.      // media sample start and stop times contain the requested absolute      // byte position (start inclusive, stop exclusive).      // may fail if sample not obtained from agreed allocator.      // may fail if start/stop position does not match agreed alignment.      // samples allocated from source pin's allocator may fail      // GetPointer until after returning from WaitForNext.      STDMETHODIMP Request(                       IMediaSample* pSample,                       DWORD_PTR dwUser);         // user context        // block until the next sample is completed or the timeout occurs.      // timeout (millisecs) may be 0 or INFINITE. Samples may not      // be delivered in order. If there is a read error of any sort, a      // notification will already have been sent by the source filter,      // and STDMETHODIMP will be an error.      STDMETHODIMP WaitForNext(                        DWORD dwTimeout,                        IMediaSample** ppSample,  // completed sample                        DWORD_PTR * pdwUser);     // user context        // sync read of data. Sample passed in must have been acquired from      // the agreed allocator. Start and stop position must be aligned.      // equivalent to a Request/WaitForNext pair, but may avoid the      // need for a thread on the source filter.      STDMETHODIMP SyncReadAligned(                        IMediaSample* pSample);          // sync read. works in stopped state as well as run state.      // need not be aligned. Will fail if read is beyond actual total      // length.      STDMETHODIMP SyncRead(                        LONGLONG llPosition,  // absolute file position                        LONG lLength,         // nr bytes required                        BYTE* pBuffer);       // write data here        // return total length of stream, and currently available length.      // reads for beyond the available length but within the total length will      // normally succeed but may block for a long period.      STDMETHODIMP Length(                        LONGLONG* pTotal,                        LONGLONG* pAvailable);        // cause all outstanding reads to return, possibly with a failure code      // (VFW_E_TIMEOUT) indicating they were cancelled.      // these are defined on IAsyncReader and IPin      STDMETHODIMP BeginFlush(void);      STDMETHODIMP EndFlush(void);    };   // CAsyncOutputPin实现了一个输出Pin // 继承自IAsyncReader、CBasePin,这是对拉模式的Source Filter的基本要求 /* IAsyncReader接口方法及描述如下: BeginFlush 放弃所有正在进行的数据读取 EndFlush 与BeginFlush配对,标示Flush过程结束 Length 得到数据总长度和当前可以读取的长度 RequestAlloctor 要求一个输入Pin上的Sample管理器 Request 发出一个数据请求 SyncReadAligned 同步读取数据(边界对齐) SyncRead 同步读取数据 WaitForNext 等待一个请求的完成 ====================================================================== 可以看出CAsyOutputPin类上实现的IAsyncReader的各个接口方法,都“委托” 给了CAsyncIo类对象的同名成员函数 */ class CAsyncOutputPin : public IAsyncReader, public CBasePin { protected: CAsyncReader* m_pReader; CAsyncIo * m_pIo; // This is set every time we're asked to return an IAsyncReader // interface // This allows us to know if the downstream pin can use // this transport, otherwise we can hook up to thinks like the // dump filter and nothing happens BOOL m_bQueriedForAsyncReader; HRESULT InitAllocator(IMemAllocator **ppAlloc); public: // constructor and destructor CAsyncOutputPin( HRESULT * phr, CAsyncReader *pReader, CAsyncIo *pIo, CCritSec * pLock); ~CAsyncOutputPin(); // --- CUnknown --- // need to expose IAsyncReader DECLARE_IUNKNOWN STDMETHODIMP NonDelegatingQueryInterface(REFIID, void**); // --- IPin methods --- STDMETHODIMP Connect( IPin * pReceivePin, const AM_MEDIA_TYPE *pmt // optional media type ); // --- CBasePin methods --- // return the types we prefer - this will return the known // file type HRESULT GetMediaType(int iPosition, CMediaType *pMediaType); // can we support this type? HRESULT CheckMediaType(const CMediaType* pType); // Clear the flag so we see if IAsyncReader is queried for HRESULT CheckConnect(IPin *pPin) { m_bQueriedForAsyncReader = FALSE; return CBasePin::CheckConnect(pPin); } // See if it was asked for HRESULT CompleteConnect(IPin *pReceivePin) { if (m_bQueriedForAsyncReader) { return CBasePin::CompleteConnect(pReceivePin); } else { #ifdef VFW_E_NO_TRANSPORT return VFW_E_NO_TRANSPORT; #else return E_FAIL; #endif } } // Remove our connection status HRESULT BreakConnect() { m_bQueriedForAsyncReader = FALSE; return CBasePin::BreakConnect(); } // --- IAsyncReader methods --- // pass in your preferred allocator and your preferred properties. // method returns the actual allocator to be used. Call GetProperties // on returned allocator to learn alignment and prefix etc chosen. // this allocator will be not be committed and decommitted by // the async reader, only by the consumer. STDMETHODIMP RequestAllocator( IMemAllocator* pPreferred, ALLOCATOR_PROPERTIES* pProps, IMemAllocator ** ppActual); // queue a request for data. // media sample start and stop times contain the requested absolute // byte position (start inclusive, stop exclusive). // may fail if sample not obtained from agreed allocator. // may fail if start/stop position does not match agreed alignment. // samples allocated from source pin's allocator may fail // GetPointer until after returning from WaitForNext. STDMETHODIMP Request( IMediaSample* pSample, DWORD_PTR dwUser); // user context // block until the next sample is completed or the timeout occurs. // timeout (millisecs) may be 0 or INFINITE. Samples may not // be delivered in order. If there is a read error of any sort, a // notification will already have been sent by the source filter, // and STDMETHODIMP will be an error. STDMETHODIMP WaitForNext( DWORD dwTimeout, IMediaSample** ppSample, // completed sample DWORD_PTR * pdwUser); // user context // sync read of data. Sample passed in must have been acquired from // the agreed allocator. Start and stop position must be aligned. // equivalent to a Request/WaitForNext pair, but may avoid the // need for a thread on the source filter. STDMETHODIMP SyncReadAligned( IMediaSample* pSample); // sync read. works in stopped state as well as run state. // need not be aligned. Will fail if read is beyond actual total // length. STDMETHODIMP SyncRead( LONGLONG llPosition, // absolute file position LONG lLength, // nr bytes required BYTE* pBuffer); // write data here // return total length of stream, and currently available length. // reads for beyond the available length but within the total length will // normally succeed but may block for a long period. STDMETHODIMP Length( LONGLONG* pTotal, LONGLONG* pAvailable); // cause all outstanding reads to return, possibly with a failure code // (VFW_E_TIMEOUT) indicating they were cancelled. // these are defined on IAsyncReader and IPin STDMETHODIMP BeginFlush(void); STDMETHODIMP EndFlush(void); };   5、 CBaseInputPin和CBaseOutputPin  从CBasePin类派生的,也是很基本的输入或输出pin。 它们的实现可参见 amfilter.cpp CBaseInputPin实现了IMemInputPin(用于推模式的数据传送), 而CBaseOutputPin主要完成了传送数据所使用的Sample管理器(Allocator)的协商,并重写了CBasePin::Active(用于实际的Sample内存分配) 以及CBasePin::Inactive(用于Sample内存的释放) class AM_NOVTABLE CBaseInputPin : public CBasePin,                                    public IMemInputPin  {    protected:        IMemAllocator *m_pAllocator;    // Default memory allocator        // allocator is read-only, so received samples      // cannot be modified (probably only relevant to in-place      // transforms      BYTE m_bReadOnly;        // in flushing state (between BeginFlush and EndFlush)      // if TRUE, all Receives are returned with S_FALSE      BYTE m_bFlushing;        // Sample properties - initalized in Receive      AM_SAMPLE2_PROPERTIES m_SampleProps;    public:        CBaseInputPin(          TCHAR *pObjectName,          CBaseFilter *pFilter,          CCritSec *pLock,          HRESULT *phr,          LPCWSTR pName);  #ifdef UNICODE      CBaseInputPin(          CHAR *pObjectName,          CBaseFilter *pFilter,          CCritSec *pLock,          HRESULT *phr,          LPCWSTR pName);  #endif      virtual ~CBaseInputPin();        DECLARE_IUNKNOWN        // override this to publicise our interfaces      STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void **ppv);        // return the allocator interface that this input pin      // would like the output pin to use      STDMETHODIMP GetAllocator(IMemAllocator ** ppAllocator);        // tell the input pin which allocator the output pin is actually      // going to use.      STDMETHODIMP NotifyAllocator(                      IMemAllocator * pAllocator,                      BOOL bReadOnly);        // do something with this media sample      STDMETHODIMP Receive(IMediaSample *pSample);        // do something with these media samples      STDMETHODIMP ReceiveMultiple (          IMediaSample **pSamples,          long nSamples,          long *nSamplesProcessed);        // See if Receive() blocks      STDMETHODIMP ReceiveCanBlock();        // Default handling for BeginFlush - call at the beginning      // of your implementation (makes sure that all Receive calls      // fail). After calling this, you need to free any queued data      // and then call downstream.      STDMETHODIMP BeginFlush(void);        // default handling for EndFlush - call at end of your implementation      // - before calling this, ensure that there is no queued data and no thread      // pushing any more without a further receive, then call downstream,      // then call this method to clear the m_bFlushing flag and re-enable      // receives      STDMETHODIMP EndFlush(void);        // this method is optional (can return E_NOTIMPL).      // default implementation returns E_NOTIMPL. Override if you have      // specific alignment or prefix needs, but could use an upstream      // allocator      STDMETHODIMP GetAllocatorRequirements(ALLOCATOR_PROPERTIES*pProps);        // Release the pin's allocator.      HRESULT BreakConnect();        // helper method to check the read-only flag      BOOL IsReadOnly() {          return m_bReadOnly;      };        // helper method to see if we are flushing      BOOL IsFlushing() {          return m_bFlushing;      };        //  Override this for checking whether it's OK to process samples      //  Also call this from EndOfStream.      virtual HRESULT CheckStreaming();        // Pass a Quality notification on to the appropriate sink      HRESULT PassNotify(Quality& q);          //================================================================================      // IQualityControl methods (from CBasePin)      //================================================================================        STDMETHODIMP Notify(IBaseFilter * pSender, Quality q);        // no need to override:      // STDMETHODIMP SetSink(IQualityControl * piqc);          // switch the pin to inactive state - may already be inactive      virtual HRESULT Inactive(void);        // Return sample properties pointer      AM_SAMPLE2_PROPERTIES * SampleProps() {          ASSERT(m_SampleProps.cbData != 0);          return &m_SampleProps;      }    };   class AM_NOVTABLE CBaseInputPin : public CBasePin, public IMemInputPin { protected: IMemAllocator *m_pAllocator; // Default memory allocator // allocator is read-only, so received samples // cannot be modified (probably only relevant to in-place // transforms BYTE m_bReadOnly; // in flushing state (between BeginFlush and EndFlush) // if TRUE, all Receives are returned with S_FALSE BYTE m_bFlushing; // Sample properties - initalized in Receive AM_SAMPLE2_PROPERTIES m_SampleProps; public: CBaseInputPin( TCHAR *pObjectName, CBaseFilter *pFilter, CCritSec *pLock, HRESULT *phr, LPCWSTR pName); #ifdef UNICODE CBaseInputPin( CHAR *pObjectName, CBaseFilter *pFilter, CCritSec *pLock, HRESULT *phr, LPCWSTR pName); #endif virtual ~CBaseInputPin(); DECLARE_IUNKNOWN // override this to publicise our interfaces STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void **ppv); // return the allocator interface that this input pin // would like the output pin to use STDMETHODIMP GetAllocator(IMemAllocator ** ppAllocator); // tell the input pin which allocator the output pin is actually // going to use. STDMETHODIMP NotifyAllocator( IMemAllocator * pAllocator, BOOL bReadOnly); // do something with this media sample STDMETHODIMP Receive(IMediaSample *pSample); // do something with these media samples STDMETHODIMP ReceiveMultiple ( IMediaSample **pSamples, long nSamples, long *nSamplesProcessed); // See if Receive() blocks STDMETHODIMP ReceiveCanBlock(); // Default handling for BeginFlush - call at the beginning // of your implementation (makes sure that all Receive calls // fail). After calling this, you need to free any queued data // and then call downstream. STDMETHODIMP BeginFlush(void); // default handling for EndFlush - call at end of your implementation // - before calling this, ensure that there is no queued data and no thread // pushing any more without a further receive, then call downstream, // then call this method to clear the m_bFlushing flag and re-enable // receives STDMETHODIMP EndFlush(void); // this method is optional (can return E_NOTIMPL). // default implementation returns E_NOTIMPL. Override if you have // specific alignment or prefix needs, but could use an upstream // allocator STDMETHODIMP GetAllocatorRequirements(ALLOCATOR_PROPERTIES*pProps); // Release the pin's allocator. HRESULT BreakConnect(); // helper method to check the read-only flag BOOL IsReadOnly() { return m_bReadOnly; }; // helper method to see if we are flushing BOOL IsFlushing() { return m_bFlushing; }; // Override this for checking whether it's OK to process samples // Also call this from EndOfStream. virtual HRESULT CheckStreaming(); // Pass a Quality notification on to the appropriate sink HRESULT PassNotify(Quality& q); //================================================================================ // IQualityControl methods (from CBasePin) //================================================================================ STDMETHODIMP Notify(IBaseFilter * pSender, Quality q); // no need to override: // STDMETHODIMP SetSink(IQualityControl * piqc); // switch the pin to inactive state - may already be inactive virtual HRESULT Inactive(void); // Return sample properties pointer AM_SAMPLE2_PROPERTIES * SampleProps() { ASSERT(m_SampleProps.cbData != 0); return &m_SampleProps; } };       class  AM_NOVTABLE CBaseOutputPin : public CBasePin  {    protected:        IMemAllocator *m_pAllocator;      IMemInputPin *m_pInputPin;        // interface on the downstreaminput pin                                        // set up in CheckConnect when we connect.    public:        CBaseOutputPin(          TCHAR *pObjectName,          CBaseFilter *pFilter,          CCritSec *pLock,          HRESULT *phr,          LPCWSTR pName);  #ifdef UNICODE      CBaseOutputPin(          CHAR *pObjectName,          CBaseFilter *pFilter,          CCritSec *pLock,          HRESULT *phr,          LPCWSTR pName);  #endif      // override CompleteConnect() so we can negotiate an allocator      virtual HRESULT CompleteConnect(IPin *pReceivePin);        // negotiate the allocator and its buffer size/count and other properties      // Calls DecideBufferSize to set properties      virtual HRESULT DecideAllocator(IMemInputPin * pPin, IMemAllocator ** pAlloc);        // override this to set the buffer size and count. Return an error      // if the size/count is not to your liking.      // The allocator properties passed in are those requested by the      // input pin - use eg the alignment and prefix members if you have      // no preference on these.      virtual HRESULT DecideBufferSize(          IMemAllocator * pAlloc,          ALLOCATOR_PROPERTIES * ppropInputRequest      ) PURE;        // returns an empty sample buffer from the allocator      virtual HRESULT GetDeliveryBuffer(IMediaSample ** ppSample,                                        REFERENCE_TIME * pStartTime,                                        REFERENCE_TIME * pEndTime,                                        DWORD dwFlags);        // deliver a filled-in sample to the connected input pin      // note - you need to release it after calling this. The receiving      // pin will addref the sample if it needs to hold it beyond the      // call.      virtual HRESULT Deliver(IMediaSample *);        // override this to control the connection      virtual HRESULT InitAllocator(IMemAllocator **ppAlloc);      HRESULT CheckConnect(IPin *pPin);      HRESULT BreakConnect();        // override to call Commit and Decommit      HRESULT Active(void);      HRESULT Inactive(void);        // we have a default handling of EndOfStream which is to return      // an error, since this should be called on input pins only      STDMETHODIMP EndOfStream(void);        // called from elsewhere in our filter to pass EOS downstream to      // our connected input pin      virtual HRESULT DeliverEndOfStream(void);        // same for Begin/EndFlush - we handle Begin/EndFlush since it      // is an error on an output pin, and we have Deliver methods to      // call the methods on the connected pin      STDMETHODIMP BeginFlush(void);      STDMETHODIMP EndFlush(void);      virtual HRESULT DeliverBeginFlush(void);      virtual HRESULT DeliverEndFlush(void);        // deliver NewSegment to connected pin - you will need to      // override this if you queue any data in your output pin.      virtual HRESULT DeliverNewSegment(                          REFERENCE_TIME tStart,                          REFERENCE_TIME tStop,                          double dRate);        //================================================================================      // IQualityControl methods      //================================================================================        // All inherited from CBasePin and not overridden here.      // STDMETHODIMP Notify(IBaseFilter * pSender, Quality q);      // STDMETHODIMP SetSink(IQualityControl * piqc);  };   class AM_NOVTABLE CBaseOutputPin : public CBasePin { protected: IMemAllocator *m_pAllocator; IMemInputPin *m_pInputPin; // interface on the downstreaminput pin // set up in CheckConnect when we connect. public: CBaseOutputPin( TCHAR *pObjectName, CBaseFilter *pFilter, CCritSec *pLock, HRESULT *phr, LPCWSTR pName); #ifdef UNICODE CBaseOutputPin( CHAR *pObjectName, CBaseFilter *pFilter, CCritSec *pLock, HRESULT *phr, LPCWSTR pName); #endif // override CompleteConnect() so we can negotiate an allocator virtual HRESULT CompleteConnect(IPin *pReceivePin); // negotiate the allocator and its buffer size/count and other properties // Calls DecideBufferSize to set properties virtual HRESULT DecideAllocator(IMemInputPin * pPin, IMemAllocator ** pAlloc); // override this to set the buffer size and count. Return an error // if the size/count is not to your liking. // The allocator properties passed in are those requested by the // input pin - use eg the alignment and prefix members if you have // no preference on these. virtual HRESULT DecideBufferSize( IMemAllocator * pAlloc, ALLOCATOR_PROPERTIES * ppropInputRequest ) PURE; // returns an empty sample buffer from the allocator virtual HRESULT GetDeliveryBuffer(IMediaSample ** ppSample, REFERENCE_TIME * pStartTime, REFERENCE_TIME * pEndTime, DWORD dwFlags); // deliver a filled-in sample to the connected input pin // note - you need to release it after calling this. The receiving // pin will addref the sample if it needs to hold it beyond the // call. virtual HRESULT Deliver(IMediaSample *); // override this to control the connection virtual HRESULT InitAllocator(IMemAllocator **ppAlloc); HRESULT CheckConnect(IPin *pPin); HRESULT BreakConnect(); // override to call Commit and Decommit HRESULT Active(void); HRESULT Inactive(void); // we have a default handling of EndOfStream which is to return // an error, since this should be called on input pins only STDMETHODIMP EndOfStream(void); // called from elsewhere in our filter to pass EOS downstream to // our connected input pin virtual HRESULT DeliverEndOfStream(void); // same for Begin/EndFlush - we handle Begin/EndFlush since it // is an error on an output pin, and we have Deliver methods to // call the methods on the connected pin STDMETHODIMP BeginFlush(void); STDMETHODIMP EndFlush(void); virtual HRESULT DeliverBeginFlush(void); virtual HRESULT DeliverEndFlush(void); // deliver NewSegment to connected pin - you will need to // override this if you queue any data in your output pin. virtual HRESULT DeliverNewSegment( REFERENCE_TIME tStart, REFERENCE_TIME tStop, double dRate); //================================================================================ // IQualityControl methods //================================================================================ // All inherited from CBasePin and not overridden here. // STDMETHODIMP Notify(IBaseFilter * pSender, Quality q); // STDMETHODIMP SetSink(IQualityControl * piqc); };    CBaseInputPin类的使用方法(派生一个子类,并且至少需要重写以下函数)如下: (1) CBaseInputPin::BeginFlush (2) CBaseInputPin::EndFlush (3) CBaseInputPin::Receive (4) CBaseInputPin::CheckMediaType (5) CBaseInputPin::GetMediaType eg: class CRendererInputPin : public CBaseInputPin  {  protected:        CBaseRenderer *m_pRenderer;    public:        CRendererInputPin(CBaseRenderer *pRenderer,                        HRESULT *phr,                        LPCWSTR Name);        // Overriden from the base pin classes        HRESULT BreakConnect();      HRESULT CompleteConnect(IPin *pReceivePin);      HRESULT SetMediaType(const CMediaType *pmt);      HRESULT CheckMediaType(const CMediaType *pmt);      HRESULT Active();      HRESULT Inactive();        // Add rendering behaviour to interface functions        STDMETHODIMP QueryId(LPWSTR *Id);      STDMETHODIMP EndOfStream();      STDMETHODIMP BeginFlush();      STDMETHODIMP EndFlush();      STDMETHODIMP Receive(IMediaSample *pMediaSample);        // Helper      IMemAllocator inline *Allocator() const      {          return m_pAllocator;      }  };   class CRendererInputPin : public CBaseInputPin { protected: CBaseRenderer *m_pRenderer; public: CRendererInputPin(CBaseRenderer *pRenderer, HRESULT *phr, LPCWSTR Name); // Overriden from the base pin classes HRESULT BreakConnect(); HRESULT CompleteConnect(IPin *pReceivePin); HRESULT SetMediaType(const CMediaType *pmt); HRESULT CheckMediaType(const CMediaType *pmt); HRESULT Active(); HRESULT Inactive(); // Add rendering behaviour to interface functions STDMETHODIMP QueryId(LPWSTR *Id); STDMETHODIMP EndOfStream(); STDMETHODIMP BeginFlush(); STDMETHODIMP EndFlush(); STDMETHODIMP Receive(IMediaSample *pMediaSample); // Helper IMemAllocator inline *Allocator() const { return m_pAllocator; } };     CBaseOutputPin类的使用方法(派生一个子类,并且最少需要重写以下函数)如下: (1) 重写CBasePin::CheckMediaType进行连接时媒体类型的检查; (2) 实现纯虚函数CBaseOutputPin::DecideBufferSize,决定Sample内存的大小; (3) 重写CBasePin::GetMediaType, 提供Pin 上的首选媒体类型。   class CTransformOutputPin : public CBaseOutputPin  {      friend class CTransformFilter;    protected:      CTransformFilter *m_pTransformFilter;    public:        // implement IMediaPosition by passing upstream      IUnknown * m_pPosition;        CTransformOutputPin(          TCHAR *pObjectName,          CTransformFilter *pTransformFilter,          HRESULT * phr,          LPCWSTR pName);  #ifdef UNICODE      CTransformOutputPin(          CHAR *pObjectName,          CTransformFilter *pTransformFilter,          HRESULT * phr,          LPCWSTR pName);  #endif      ~CTransformOutputPin();        // override to expose IMediaPosition      STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void **ppv);        // --- CBaseOutputPin ------------        STDMETHODIMP QueryId(LPWSTR * Id)      {          return AMGetWideString(L"Out", Id);      }        // Grab and release extra interfaces if required        HRESULT CheckConnect(IPin *pPin);      HRESULT BreakConnect();      HRESULT CompleteConnect(IPin *pReceivePin);        // check that we can support this output type      HRESULT CheckMediaType(const CMediaType* mtOut);        // set the connection media type      HRESULT SetMediaType(const CMediaType *pmt);        // called from CBaseOutputPin during connection to ask for      // the count and size of buffers we need.      HRESULT DecideBufferSize(                  IMemAllocator * pAlloc,                  ALLOCATOR_PROPERTIES *pProp);        // returns the preferred formats for a pin      HRESULT GetMediaType(int iPosition,CMediaType *pMediaType);        // inherited from IQualityControl via CBasePin      STDMETHODIMP Notify(IBaseFilter * pSender, Quality q);        // Media type  public:      CMediaType& CurrentMediaType() { return m_mt; };  };   class CTransformOutputPin : public CBaseOutputPin { friend class CTransformFilter; protected: CTransformFilter *m_pTransformFilter; public: // implement IMediaPosition by passing upstream IUnknown * m_pPosition; CTransformOutputPin( TCHAR *pObjectName, CTransformFilter *pTransformFilter, HRESULT * phr, LPCWSTR pName); #ifdef UNICODE CTransformOutputPin( CHAR *pObjectName, CTransformFilter *pTransformFilter, HRESULT * phr, LPCWSTR pName); #endif ~CTransformOutputPin(); // override to expose IMediaPosition STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void **ppv); // --- CBaseOutputPin ------------ STDMETHODIMP QueryId(LPWSTR * Id) { return AMGetWideString(L"Out", Id); } // Grab and release extra interfaces if required HRESULT CheckConnect(IPin *pPin); HRESULT BreakConnect(); HRESULT CompleteConnect(IPin *pReceivePin); // check that we can support this output type HRESULT CheckMediaType(const CMediaType* mtOut); // set the connection media type HRESULT SetMediaType(const CMediaType *pmt); // called from CBaseOutputPin during connection to ask for // the count and size of buffers we need. HRESULT DecideBufferSize( IMemAllocator * pAlloc, ALLOCATOR_PROPERTIES *pProp); // returns the preferred formats for a pin HRESULT GetMediaType(int iPosition,CMediaType *pMediaType); // inherited from IQualityControl via CBasePin STDMETHODIMP Notify(IBaseFilter * pSender, Quality q); // Media type public: CMediaType& CurrentMediaType() { return m_mt; }; };    =================================================================== 如果开发的是一个Transform Filter,Filter的父类很多时候都是选择CTransformFilter或CTransInPlaceFilter,这种Filter的开发相对简单。 但有时,Filter框架不得不选择CBaseFilter、 CBaseInputPin、CBaseOutputFilter等类来实现,这就有点麻烦了。 这时候可以参考CTransformFilter、CTransformInputPin、CTransformOutputPin对上述3上基类的使用,以此来指导Filter的开发。  =================================================================== 6、 CSource DirectShow SDK还提供了其他更加实用的Filter类,如: CSource、CTransformFilter、CTransInPlaceFilter、CVideoTransformFilter、 CBaseRender、CBase Video Render等。 它们的继承关系如图: 如上图所示,CSource类(参见source.cpp的实现)直接从CaseFilter中继承而来,一般作为推模式Source Filter的父类。 CSource类的使用方法如下: (1)从CSource类中派生一个新的Filter类; (2)在新的Filter类的构造函数中创建各个CSourceStream类实例(CSourceStream类的构造函数会自动将该Pin加入Filter中,并在析构函数中自动删除); (3)使用CSource::pStateLock函数返回的同步对象进行Filter对象上的多线程同步。 注意: 使用CSource作为Filter父类的Filter未必就是Source Filter。在有些开发Transform Filter的应用中,输出Pin需要使用独立的线程。(即与输入Pin上传送数据               不同的线程)传关,也可以考虑使用CSource。 eg: 参照我的另一篇文章:   class CPushSourceBitmap : public CSource  {    private:      // Constructor is private because you have to use CreateInstance      CPushSourceBitmap(IUnknown *pUnk, HRESULT *phr);      ~CPushSourceBitmap();        CPushPinBitmap *m_pPin;    public:      static CUnknown * WINAPI CreateInstance(IUnknown *pUnk, HRESULT *phr);      };   class CPushSourceBitmap : public CSource { private: // Constructor is private because you have to use CreateInstance CPushSourceBitmap(IUnknown *pUnk, HRESULT *phr); ~CPushSourceBitmap(); CPushPinBitmap *m_pPin; public: static CUnknown * WINAPI CreateInstance(IUnknown *pUnk, HRESULT *phr); };     CPushSourceBitmap::CPushSourceBitmap(IUnknown *pUnk, HRESULT *phr)             : CSource(NAME("PushSourceBitmap"), pUnk, CLSID_PushSourceBitmap)  {      // The pin magically adds itself to our pin array.      m_pPin = new CPushPinBitmap(phr, this);        if (phr)      {          if (m_pPin == NULL)              *phr = E_OUTOFMEMORY;          else              *phr = S_OK;      }    }   CPushSourceBitmap::CPushSourceBitmap(IUnknown *pUnk, HRESULT *phr) : CSource(NAME("PushSourceBitmap"), pUnk, CLSID_PushSourceBitmap) { // The pin magically adds itself to our pin array. m_pPin = new CPushPinBitmap(phr, this); if (phr) { if (m_pPin == NULL) *phr = E_OUTOFMEMORY; else *phr = S_OK; } }   7 、  CSourceStream CSource实际上继承自CBaseFilter,提供了一个“推”数据的能力,这种Filter至少有一个输出 Pin采用了CSourecStream类(或CSourceStream的子类)。如下图所示: CSourceStream上实现了一个线程(CSourceStream从CAMThread类继承而来),Sample数据就是靠这个线程向一线Filter发送的。 CSourceStream类的使用方法如下: (1)从CSourceStream派生一个输出Pin类; (2)重写CSourceStream::GetMediaType,提供输出Pin上的首选媒体类型; (3)重写CSourceStream::CheckMediaType,进行连续时媒体类型的检查;(可选) (4)实现CBaseOutPin::DecideBufferSize,决定Sample内存的大小; (5)实现CSourceStream::FillBuffer,为即将传送出去的Sample 填充数据; (6)可选地实现CSourceStream::OnThreadCreate、CSourceSream::OnThreadDestroy、CSourceStream::OnThreadStartPlay等函数, 进行适当时节的初始化、资源管理等操作。 eg: 参照我的另一篇文章:   class CPushPinBitmap : public CSourceStream  {  protected:        int m_FramesWritten;                // To track where we are in the file      BOOL m_bZeroMemory;                 // Do we need to clear the buffer?      CRefTime m_rtSampleTime;            // The time stamp for each sample        BITMAPINFO *m_pBmi;                 // Pointer to the bitmap header      DWORD       m_cbBitmapInfo;         // Size of the bitmap header            // File opening variables       HANDLE m_hFile;                     // Handle returned from CreateFile      BYTE * m_pFile;                     // Points to beginning of file buffer      BYTE * m_pImage;                    // Points to pixel bits                                              int m_iFrameNumber;      const REFERENCE_TIME m_rtFrameLength;        CCritSec m_cSharedState;            // Protects our internal state      CImageDisplay m_Display;            // Figures out our media type for us    public:        CPushPinBitmap(HRESULT *phr, CSource *pFilter);      ~CPushPinBitmap();        // Override the version that offers exactly one media type      HRESULT GetMediaType(CMediaType *pMediaType);      HRESULT DecideBufferSize(IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *pRequest);      HRESULT FillBuffer(IMediaSample *pSample);            // Quality control      // Not implemented because we aren't going in real time.      // If the file-writing filter slows the graph down, we just do nothing, which means      // wait until we're unblocked. No frames are ever dropped.      STDMETHODIMP Notify(IBaseFilter *pSelf, Quality q)      {          return E_FAIL;      }    };   class CPushPinBitmap : public CSourceStream { protected: int m_FramesWritten; // To track where we are in the file BOOL m_bZeroMemory; // Do we need to clear the buffer? CRefTime m_rtSampleTime; // The time stamp for each sample BITMAPINFO *m_pBmi; // Pointer to the bitmap header DWORD m_cbBitmapInfo; // Size of the bitmap header // File opening variables HANDLE m_hFile; // Handle returned from CreateFile BYTE * m_pFile; // Points to beginning of file buffer BYTE * m_pImage; // Points to pixel bits int m_iFrameNumber; const REFERENCE_TIME m_rtFrameLength; CCritSec m_cSharedState; // Protects our internal state CImageDisplay m_Display; // Figures out our media type for us public: CPushPinBitmap(HRESULT *phr, CSource *pFilter); ~CPushPinBitmap(); // Override the version that offers exactly one media type HRESULT GetMediaType(CMediaType *pMediaType); HRESULT DecideBufferSize(IMemAllocator *pAlloc, ALLOCATOR_PROPERTIES *pRequest); HRESULT FillBuffer(IMediaSample *pSample); // Quality control // Not implemented because we aren't going in real time. // If the file-writing filter slows the graph down, we just do nothing, which means // wait until we're unblocked. No frames are ever dropped. STDMETHODIMP Notify(IBaseFilter *pSelf, Quality q) { return E_FAIL; } };   8、 CTransformFilter  CTransformFilter类是开发Transform Filter最基本的类,也是最常用到的类。结构如下: 它有一个输入Pin和一个输出Pin,分别使用CTransformInputPin类和CTransformOutputPin类。   从图4.8和图4.9可以看出, CTransformFilter从CBaseFilter继承而来, CTransformInputPin从CBaseInputPin继承而来, CTransformOutputPin从CBaseOutputPin继承而来。另个,在CTransformOutputPin上还实现了IMdiaSeeking 和 IMediaPosition接口。 (其实,CTransformOutputPin并没有真正实现各个Seek操作。在实际的Seek操作请发生时,CTransformOutpPin会将这些操作请求转发给上一级Filter的输出Pin)。 CTransformFilter实现的最大特征是,它将Pin上必须实现的函数都“委托”到了Filter上(Pin上必须实现的函数在Filter上有类似的函数定义)。 一般无须重写输入和输出Pin类,而只须在Filter上实现相应的函数就行了)。 提示:CTransformFilter默认在GetPin函数实现中创建输入和输出Pin。因此,如果重写了自己的输入或输出Pin类,需要重写GetPin函数。 CTransformFilter类的使用方法(派生一个Filter子类,且最少需要重写以下函数): (1)CTransformFilter::CheckInputType (2)CTransformFilter::CheckTransform (3)CTransformFilter::DecideBufferSize (4)CTransformFilter::GetMeiaType (5)CTransformFilter::Transform eg:CVideoTransformFilter虽然没有实现上面五个函数,但CVideoTransformFilter 的继承类去实现它们。 class CVideoTransformFilter : public CTransformFilter  {    public:        CVideoTransformFilter(TCHAR *, LPUNKNOWN, REFCLSID clsid);      ~CVideoTransformFilter();      HRESULT EndFlush();        // =================================================================      // ----- override these bits ---------------------------------------      // =================================================================      // The following methods are in CTransformFilter which is inherited.      // They are mentioned here for completeness      //      // These MUST be supplied in a derived class      //      // NOTE:      // virtual HRESULT Transform(IMediaSample * pIn, IMediaSample *pOut);      // virtual HRESULT CheckInputType(const CMediaType* mtIn) PURE;      // virtual HRESULT CheckTransform      //     (const CMediaType* mtIn, const CMediaType* mtOut) PURE;      // static CCOMObject * CreateInstance(LPUNKNOWN, HRESULT *);      // virtual HRESULT DecideBufferSize      //     (IMemAllocator * pAllocator, ALLOCATOR_PROPERTIES *pprop) PURE;      // virtual HRESULT GetMediaType(int iPosition, CMediaType *pMediaType) PURE;      //      // These MAY also be overridden      //      // virtual HRESULT StopStreaming();      // virtual HRESULT SetMediaType(PIN_DIRECTION direction,const CMediaType *pmt);      // virtual HRESULT CheckConnect(PIN_DIRECTION dir,IPin *pPin);      // virtual HRESULT BreakConnect(PIN_DIRECTION dir);      // virtual HRESULT CompleteConnect(PIN_DIRECTION direction,IPin *pReceivePin);      // virtual HRESULT EndOfStream(void);      // virtual HRESULT BeginFlush(void);      // virtual HRESULT EndFlush(void);      // virtual HRESULT NewSegment      //     (REFERENCE_TIME tStart,REFERENCE_TIME tStop,double dRate);  #ifdef PERF        // If you override this - ensure that you register all these ids      // as well as any of your own,      virtual void RegisterPerfId() {          m_idSkip        = MSR_REGISTER(TEXT("Video Transform Skip frame"));          m_idFrameType   = MSR_REGISTER(TEXT("Video transform frame type"));          m_idLate        = MSR_REGISTER(TEXT("Video Transform Lateness"));          m_idTimeTillKey = MSR_REGISTER(TEXT("Video Transform Estd. time to next key"));          CTransformFilter::RegisterPerfId();      }  #endif      protected:        // =========== QUALITY MANAGEMENT IMPLEMENTATION ========================      // Frames are assumed to come in three types:      // Type 1: an AVI key frame or an MPEG I frame.      //        This frame can be decoded with no history.      //        Dropping this frame means that no further frame can be decoded      //        until the next type 1 frame.      //        Type 1 frames are sync points.      // Type 2: an AVI non-key frame or an MPEG P frame.      //        This frame cannot be decoded unless the previous type 1 frame was      //        decoded and all type 2 frames since have been decoded.      //        Dropping this frame means that no further frame can be decoded      //        until the next type 1 frame.      // Type 3: An MPEG B frame.      //        This frame cannot be decoded unless the previous type 1 or 2 frame      //        has been decoded AND the subsequent type 1 or 2 frame has also      //        been decoded.  (This requires decoding the frames out of sequence).      //        Dropping this frame affects no other frames.  This implementation      //        does not allow for these.  All non-sync-point frames are treated      //        as being type 2.      //      // The spacing of frames of type 1 in a file is not guaranteed.  There MUST      // be a type 1 frame at (well, near) the start of the file in order to start      // decoding at all.  After that there could be one every half second or so,      // there could be one at the start of each scene (aka "cut", "shot") or      // there could be no more at all.      // If there is only a single type 1 frame then NO FRAMES CAN BE DROPPED      // without losing all the rest of the movie.  There is no way to tell whether      // this is the case, so we find that we are in the gambling business.      // To try to improve the odds, we record the greatest interval between type 1s      // that we have seen and we bet on things being no worse than this in the      // future.        // You can tell if it's a type 1 frame by calling IsSyncPoint().      // there is no architected way to test for a type 3, so you should override      // the quality management here if you have B-frames.        int m_nKeyFramePeriod; // the largest observed interval between type 1 frames                             // 1 means every frame is type 1, 2 means every other.        int m_nFramesSinceKeyFrame; // Used to count frames since the last type 1.                                  // becomes the new m_nKeyFramePeriod if greater.        BOOL m_bSkipping;           // we are skipping to the next type 1 frame    #ifdef PERF      int m_idFrameType;          // MSR id Frame type.  1=Key, 2="non-key"      int m_idSkip;               // MSR id skipping      int m_idLate;               // MSR id lateness      int m_idTimeTillKey;        // MSR id for guessed time till next key frame.  #endif        virtual HRESULT StartStreaming();        HRESULT AbortPlayback(HRESULT hr);  // if something bad happens        HRESULT Receive(IMediaSample *pSample);        HRESULT AlterQuality(Quality q);        BOOL ShouldSkipFrame(IMediaSample * pIn);        int m_itrLate;              // lateness from last Quality message                                  // (this overflows at 214 secs late).      int m_tDecodeStart;         // timeGetTime when decode started.      int m_itrAvgDecode;         // Average decode time in reference units.        BOOL m_bNoSkip;             // debug - no skipping.        // We send an EC_QUALITY_CHANGE notification to the app if we have to degrade.      // We send one when we start degrading, not one for every frame, this means      // we track whether we've sent one yet.      BOOL m_bQualityChanged;        // When non-zero, don't pass anything to renderer until next keyframe      // If there are few keys, give up and eventually draw something      int m_nWaitForKey;  };   class CVideoTransformFilter : public CTransformFilter { public: CVideoTransformFilter(TCHAR *, LPUNKNOWN, REFCLSID clsid); ~CVideoTransformFilter(); HRESULT EndFlush(); // ================================================================= // ----- override these bits --------------------------------------- // ================================================================= // The following methods are in CTransformFilter which is inherited. // They are mentioned here for completeness // // These MUST be supplied in a derived class // // NOTE: // virtual HRESULT Transform(IMediaSample * pIn, IMediaSample *pOut); // virtual HRESULT CheckInputType(const CMediaType* mtIn) PURE; // virtual HRESULT CheckTransform // (const CMediaType* mtIn, const CMediaType* mtOut) PURE; // static CCOMObject * CreateInstance(LPUNKNOWN, HRESULT *); // virtual HRESULT DecideBufferSize // (IMemAllocator * pAllocator, ALLOCATOR_PROPERTIES *pprop) PURE; // virtual HRESULT GetMediaType(int iPosition, CMediaType *pMediaType) PURE; // // These MAY also be overridden // // virtual HRESULT StopStreaming(); // virtual HRESULT SetMediaType(PIN_DIRECTION direction,const CMediaType *pmt); // virtual HRESULT CheckConnect(PIN_DIRECTION dir,IPin *pPin); // virtual HRESULT BreakConnect(PIN_DIRECTION dir); // virtual HRESULT CompleteConnect(PIN_DIRECTION direction,IPin *pReceivePin); // virtual HRESULT EndOfStream(void); // virtual HRESULT BeginFlush(void); // virtual HRESULT EndFlush(void); // virtual HRESULT NewSegment // (REFERENCE_TIME tStart,REFERENCE_TIME tStop,double dRate); #ifdef PERF // If you override this - ensure that you register all these ids // as well as any of your own, virtual void RegisterPerfId() { m_idSkip = MSR_REGISTER(TEXT("Video Transform Skip frame")); m_idFrameType = MSR_REGISTER(TEXT("Video transform frame type")); m_idLate = MSR_REGISTER(TEXT("Video Transform Lateness")); m_idTimeTillKey = MSR_REGISTER(TEXT("Video Transform Estd. time to next key")); CTransformFilter::RegisterPerfId(); } #endif protected: // =========== QUALITY MANAGEMENT IMPLEMENTATION ======================== // Frames are assumed to come in three types: // Type 1: an AVI key frame or an MPEG I frame. // This frame can be decoded with no history. // Dropping this frame means that no further frame can be decoded // until the next type 1 frame. // Type 1 frames are sync points. // Type 2: an AVI non-key frame or an MPEG P frame. // This frame cannot be decoded unless the previous type 1 frame was // decoded and all type 2 frames since have been decoded. // Dropping this frame means that no further frame can be decoded // until the next type 1 frame. // Type 3: An MPEG B frame. // This frame cannot be decoded unless the previous type 1 or 2 frame // has been decoded AND the subsequent type 1 or 2 frame has also // been decoded. (This requires decoding the frames out of sequence). // Dropping this frame affects no other frames. This implementation // does not allow for these. All non-sync-point frames are treated // as being type 2. // // The spacing of frames of type 1 in a file is not guaranteed. There MUST // be a type 1 frame at (well, near) the start of the file in order to start // decoding at all. After that there could be one every half second or so, // there could be one at the start of each scene (aka "cut", "shot") or // there could be no more at all. // If there is only a single type 1 frame then NO FRAMES CAN BE DROPPED // without losing all the rest of the movie. There is no way to tell whether // this is the case, so we find that we are in the gambling business. // To try to improve the odds, we record the greatest interval between type 1s // that we have seen and we bet on things being no worse than this in the // future. // You can tell if it's a type 1 frame by calling IsSyncPoint(). // there is no architected way to test for a type 3, so you should override // the quality management here if you have B-frames. int m_nKeyFramePeriod; // the largest observed interval between type 1 frames // 1 means every frame is type 1, 2 means every other. int m_nFramesSinceKeyFrame; // Used to count frames since the last type 1. // becomes the new m_nKeyFramePeriod if greater. BOOL m_bSkipping; // we are skipping to the next type 1 frame #ifdef PERF int m_idFrameType; // MSR id Frame type. 1=Key, 2="non-key" int m_idSkip; // MSR id skipping int m_idLate; // MSR id lateness int m_idTimeTillKey; // MSR id for guessed time till next key frame. #endif virtual HRESULT StartStreaming(); HRESULT AbortPlayback(HRESULT hr); // if something bad happens HRESULT Receive(IMediaSample *pSample); HRESULT AlterQuality(Quality q); BOOL ShouldSkipFrame(IMediaSample * pIn); int m_itrLate; // lateness from last Quality message // (this overflows at 214 secs late). int m_tDecodeStart; // timeGetTime when decode started. int m_itrAvgDecode; // Average decode time in reference units. BOOL m_bNoSkip; // debug - no skipping. // We send an EC_QUALITY_CHANGE notification to the app if we have to degrade. // We send one when we start degrading, not one for every frame, this means // we track whether we've sent one yet. BOOL m_bQualityChanged; // When non-zero, don't pass anything to renderer until next keyframe // If there are few keys, give up and eventually draw something int m_nWaitForKey; };     9、 CTransInPlaceFilter CTransInPlaceFilter是一个“就地”处理的Transform Filter类。结构如下: 与CTransformFilter,CTransInPlaceFilter也有一个输入Pin和一个输出Pin,但使用CTransInPlaceOutputPin类。   CTransInPlaceFilter的输入和输出Pin上一般使用相同的媒体类型进行连接,并且使用同一个Sample管理器(如果Filter实现时要修改Sample数据, 而协商达成一致的Sample管理器只读的,那么CTransInPlaceFilter的输入和输出Pin将不得不使用各自的Sample管理器)。 CTransInPlaceFilter类要实现上述的目标,主要依赖于CTransInPlaceFilter::CompleteConnect、CTransInPlaceInputPin::GetAllocator和 CTransInPlaceInputPin::NotifyAlocator的函数实现。代码如下: // 当输入或输出Pin完成连接时被调用,  // 经过一个反复重连的过程,来达到输入和输出Pin使用相同的媒体类型的目的  HRESULT CTransInPlaceFilter::CompleteConnect(PIN_DIRECTION dir,IPin *pReceivePin)  {      UNREFERENCED_PARAMETER(pReceivePin);      ASSERT(m_pInput);      ASSERT(m_pOutput);        // if we are not part of a graph, then don't indirect the pointer      // this probably prevents use of the filter without a filtergraph      if (!m_pGraph) {          return VFW_E_NOT_IN_GRAPH;      }        // Always reconnect the input to account for buffering changes      //      // Because we don't get to suggest a type on ReceiveConnection      // we need another way of making sure the right type gets used.      //      // One way would be to have our EnumMediaTypes return our output      // connection type first but more deterministic and simple is to      // call ReconnectEx passing the type we want to reconnect with      // via the base class ReconeectPin method.        // 当输出Pin调用该函数(并且此时输入Pin已连上)时,使用输出Pin上的媒体类型对      // 输入Pin进行重连接      if (dir == PINDIR_OUTPUT) {          if( m_pInput->IsConnected() ) {              return ReconnectPin( m_pInput, &m_pOutput->CurrentMediaType() );          }          return NOERROR;      }        ASSERT(dir == PINDIR_INPUT);        // Reconnect output if necessary        // 当输入Pin调用该函数(并且此时输出Pin已连上)时,如果输入和输出Pin上使用的      // 媒体类型不一致,则使用输入Pin上的媒体类型对输出Pin进行重新连接      if( m_pOutput->IsConnected() ) {            if (  m_pInput->CurrentMediaType()             != m_pOutput->CurrentMediaType()             ) {              return ReconnectPin( m_pOutput, &m_pInput->CurrentMediaType() );          }      }      return NOERROR;    } // ComnpleteConnect   // 当输入或输出Pin完成连接时被调用, // 经过一个反复重连的过程,来达到输入和输出Pin使用相同的媒体类型的目的 HRESULT CTransInPlaceFilter::CompleteConnect(PIN_DIRECTION dir,IPin *pReceivePin) { UNREFERENCED_PARAMETER(pReceivePin); ASSERT(m_pInput); ASSERT(m_pOutput); // if we are not part of a graph, then don't indirect the pointer // this probably prevents use of the filter without a filtergraph if (!m_pGraph) { return VFW_E_NOT_IN_GRAPH; } // Always reconnect the input to account for buffering changes // // Because we don't get to suggest a type on ReceiveConnection // we need another way of making sure the right type gets used. // // One way would be to have our EnumMediaTypes return our output // connection type first but more deterministic and simple is to // call ReconnectEx passing the type we want to reconnect with // via the base class ReconeectPin method. // 当输出Pin调用该函数(并且此时输入Pin已连上)时,使用输出Pin上的媒体类型对 // 输入Pin进行重连接 if (dir == PINDIR_OUTPUT) { if( m_pInput->IsConnected() ) { return ReconnectPin( m_pInput, &m_pOutput->CurrentMediaType() ); } return NOERROR; } ASSERT(dir == PINDIR_INPUT); // Reconnect output if necessary // 当输入Pin调用该函数(并且此时输出Pin已连上)时,如果输入和输出Pin上使用的 // 媒体类型不一致,则使用输入Pin上的媒体类型对输出Pin进行重新连接 if( m_pOutput->IsConnected() ) { if ( m_pInput->CurrentMediaType() != m_pOutput->CurrentMediaType() ) { return ReconnectPin( m_pOutput, &m_pInput->CurrentMediaType() ); } } return NOERROR; } // ComnpleteConnect      // 当上一级Filter的输出Pin要求我们的输入Pin提供Sample管理器时,  // 如果我们的输出Pin已连接上,则可以取出输出Pin上的Sample管理器提供给上一级  // Filter,以此达到我们的输入和输出Pin使用同一个Sample管理器的目的  STDMETHODIMP CTransInPlaceInputPin::GetAllocator(IMemAllocator ** ppAllocator)  {      CheckPointer(ppAllocator,E_POINTER);      ValidateReadWritePtr(ppAllocator,sizeof(IMemAllocator *));      CAutoLock cObjectLock(m_pLock);        HRESULT hr;        if ( m_pTIPFilter->m_pOutput->IsConnected() ) {          //  Store the allocator we got          hr = m_pTIPFilter->OutputPin()->ConnectedIMemInputPin()                                          ->GetAllocator( ppAllocator );          if (SUCCEEDED(hr)) {              m_pTIPFilter->OutputPin()->SetAllocator( *ppAllocator );          }      }      else {          //  Help upstream filter (eg TIP filter which is having to do a copy)          //  by providing a temp allocator here - we'll never use          //  this allocator because when our output is connected we'll          //  reconnect this pin          hr = CTransformInputPin::GetAllocator( ppAllocator );      }      return hr;    } // GetAllocator   // 当上一级Filter的输出Pin要求我们的输入Pin提供Sample管理器时, // 如果我们的输出Pin已连接上,则可以取出输出Pin上的Sample管理器提供给上一级 // Filter,以此达到我们的输入和输出Pin使用同一个Sample管理器的目的 STDMETHODIMP CTransInPlaceInputPin::GetAllocator(IMemAllocator ** ppAllocator) { CheckPointer(ppAllocator,E_POINTER); ValidateReadWritePtr(ppAllocator,sizeof(IMemAllocator *)); CAutoLock cObjectLock(m_pLock); HRESULT hr; if ( m_pTIPFilter->m_pOutput->IsConnected() ) { // Store the allocator we got hr = m_pTIPFilter->OutputPin()->ConnectedIMemInputPin() ->GetAllocator( ppAllocator ); if (SUCCEEDED(hr)) { m_pTIPFilter->OutputPin()->SetAllocator( *ppAllocator ); } } else { // Help upstream filter (eg TIP filter which is having to do a copy) // by providing a temp allocator here - we'll never use // this allocator because when our output is connected we'll // reconnect this pin hr = CTransformInputPin::GetAllocator( ppAllocator ); } return hr; } // GetAllocator      // 上一级Filter调用该函数,告知输入Pin上到底使用哪一个Sample管理器  // 如果设置进来的Sample管理器是只读的,而我们在Filter中又想修改数据,  // 则我们的Filter不得不最终使用不同的Sample管理器  STDMETHODIMP  CTransInPlaceInputPin::NotifyAllocator(      IMemAllocator * pAllocator,      BOOL bReadOnly)  {      HRESULT hr = S_OK;      CheckPointer(pAllocator,E_POINTER);      ValidateReadPtr(pAllocator,sizeof(IMemAllocator));        CAutoLock cObjectLock(m_pLock);        m_bReadOnly = bReadOnly;      //  If we modify data then don't accept the allocator if it's      //  the same as the output pin's allocator        //  If our output is not connected just accept the allocator      //  We're never going to use this allocator because when our      //  output pin is connected we'll reconnect this pin      if (!m_pTIPFilter->OutputPin()->IsConnected()) {          return CTransformInputPin::NotifyAllocator(pAllocator, bReadOnly);      }        //  If the allocator is read-only and we're modifying data      //  and the allocator is the same as the output pin's      //  then reject      if (bReadOnly && m_pTIPFilter->m_bModifiesData) {          IMemAllocator *pOutputAllocator =              m_pTIPFilter->OutputPin()->PeekAllocator();            //  Make sure we have an output allocator          if (pOutputAllocator == NULL) {              hr = m_pTIPFilter->OutputPin()->ConnectedIMemInputPin()->                                        GetAllocator(&pOutputAllocator);              if(FAILED(hr)) {                  hr = CreateMemoryAllocator(&pOutputAllocator);              }              if (SUCCEEDED(hr)) {                  m_pTIPFilter->OutputPin()->SetAllocator(pOutputAllocator);                  pOutputAllocator->Release();              }          }          if (pAllocator == pOutputAllocator) {              hr = E_FAIL;          } else if(SUCCEEDED(hr)) {              //  Must copy so set the allocator properties on the output              ALLOCATOR_PROPERTIES Props, Actual;              hr = pAllocator->GetProperties(&Props);              if (SUCCEEDED(hr)) {                  hr = pOutputAllocator->SetProperties(&Props, &Actual);              }              if (SUCCEEDED(hr)) {                  if (  (Props.cBuffers > Actual.cBuffers)                     || (Props.cbBuffer > Actual.cbBuffer)                     || (Props.cbAlign  > Actual.cbAlign)                     ) {                      hr =  E_FAIL;                  }              }                //  Set the allocator on the output pin              if (SUCCEEDED(hr)) {                  hr = m_pTIPFilter->OutputPin()->ConnectedIMemInputPin()                                         ->NotifyAllocator( pOutputAllocator, FALSE );              }          }      } else {          hr = m_pTIPFilter->OutputPin()->ConnectedIMemInputPin()                                     ->NotifyAllocator( pAllocator, bReadOnly );          if (SUCCEEDED(hr)) {              m_pTIPFilter->OutputPin()->SetAllocator( pAllocator );          }      }        if (SUCCEEDED(hr)) {            // It's possible that the old and the new are the same thing.          // AddRef before release ensures that we don't unload it.          pAllocator->AddRef();            if( m_pAllocator != NULL )              m_pAllocator->Release();            m_pAllocator = pAllocator;    // We have an allocator for the input pin      }        return hr;    } // NotifyAllocator   // 上一级Filter调用该函数,告知输入Pin上到底使用哪一个Sample管理器 // 如果设置进来的Sample管理器是只读的,而我们在Filter中又想修改数据, // 则我们的Filter不得不最终使用不同的Sample管理器 STDMETHODIMP CTransInPlaceInputPin::NotifyAllocator( IMemAllocator * pAllocator, BOOL bReadOnly) { HRESULT hr = S_OK; CheckPointer(pAllocator,E_POINTER); ValidateReadPtr(pAllocator,sizeof(IMemAllocator)); CAutoLock cObjectLock(m_pLock); m_bReadOnly = bReadOnly; // If we modify data then don't accept the allocator if it's // the same as the output pin's allocator // If our output is not connected just accept the allocator // We're never going to use this allocator because when our // output pin is connected we'll reconnect this pin if (!m_pTIPFilter->OutputPin()->IsConnected()) { return CTransformInputPin::NotifyAllocator(pAllocator, bReadOnly); } // If the allocator is read-only and we're modifying data // and the allocator is the same as the output pin's // then reject if (bReadOnly && m_pTIPFilter->m_bModifiesData) { IMemAllocator *pOutputAllocator = m_pTIPFilter->OutputPin()->PeekAllocator(); // Make sure we have an output allocator if (pOutputAllocator == NULL) { hr = m_pTIPFilter->OutputPin()->ConnectedIMemInputPin()-> GetAllocator(&pOutputAllocator); if(FAILED(hr)) { hr = CreateMemoryAllocator(&pOutputAllocator); } if (SUCCEEDED(hr)) { m_pTIPFilter->OutputPin()->SetAllocator(pOutputAllocator); pOutputAllocator->Release(); } } if (pAllocator == pOutputAllocator) { hr = E_FAIL; } else if(SUCCEEDED(hr)) { // Must copy so set the allocator properties on the output ALLOCATOR_PROPERTIES Props, Actual; hr = pAllocator->GetProperties(&Props); if (SUCCEEDED(hr)) { hr = pOutputAllocator->SetProperties(&Props, &Actual); } if (SUCCEEDED(hr)) { if ( (Props.cBuffers > Actual.cBuffers) || (Props.cbBuffer > Actual.cbBuffer) || (Props.cbAlign > Actual.cbAlign) ) { hr = E_FAIL; } } // Set the allocator on the output pin if (SUCCEEDED(hr)) { hr = m_pTIPFilter->OutputPin()->ConnectedIMemInputPin() ->NotifyAllocator( pOutputAllocator, FALSE ); } } } else { hr = m_pTIPFilter->OutputPin()->ConnectedIMemInputPin() ->NotifyAllocator( pAllocator, bReadOnly ); if (SUCCEEDED(hr)) { m_pTIPFilter->OutputPin()->SetAllocator( pAllocator ); } } if (SUCCEEDED(hr)) { // It's possible that the old and the new are the same thing. // AddRef before release ensures that we don't unload it. pAllocator->AddRef(); if( m_pAllocator != NULL ) m_pAllocator->Release(); m_pAllocator = pAllocator; // We have an allocator for the input pin } return hr; } // NotifyAllocator   CTransInPlaceFilter类定义了一个成员变量m_bModifiesData ,用于指示我们在Filter中是否会修改Saple 数据。 这个变量在CTransInPlaceFilter构造函数调用时被默认初始化为true。如果我们确定不会在Filter中修改Sample数据, 那么,将m_bModifiesData设置为false, 可以保证输入和输出Pin连接完成后使用同一个Sample管理器。   10、 CVideoTransformFilter CVieoTransformFilter是一个实现了视频的质量控制的Transform Filter类。其结构如下: CVieoTransformFilter通过输入Pin上的Receive 函数接收Sample时,能够根据质量消息决定是否丢帧。这个类主要是为开发AVI解码Filter而设计的。 CVieoTransformFilter类的使用基本上与CTransformFilter相同。   11、 CBaseRenderer CBaseRender是最基本的实现Renderer Filter的类。它默认实现了一个使用CRendererInputPin类的输入Pin(Renderer Filter没有输出Pin)。 这两个类的结构如下: 从图中可以看出,CBaseRenderer从CBaseFilter继承而来。另外,CBaseRenderer上还实现了IMediaSeekin和IMediaPosition接口。 CRendererInputPin从CBaseInputPin 继承而来,它把各个主要函数调用都“委托”到Filter上。值得注意的是,当输入Pin接收到EndOfStream调用时, Renderer Filter 有责任向Filter Graph Manager发送一个EC_COMPLETE事件。 CBaseRenderer类的使用方法(派生一个子类,并至少实现如下函数)如下: (1)CBaseRenderer::CheckMediaType,用于检查输入Pin连接用的媒体类型; (2)CBaseRenderer::DoRenderSample,处理当前的Sample。 提示:CBaseRenderer实际上是为了用于播放的Render Filter设计的,对于Sample的安排比较复杂。 如果我们要开发Renderer Filter不播放Sample(比如写文件的Filter、或者负责网络的Filter),Fitler的基类可以选择CBaseFilter,而此时输入Pin最 好选择CRenderedInputPin类派生。   12、CBaseVideoRenderer CBaseVideoRenderer是一个实现Video Renderer类的基类,结构如下: CBaseVideoRenderer在CBaseRenderer的基础上增加了IQualityControl和IQualProp接口的实现。 其中IQualityControl用于视频质量控制,IQualProp用于在Filter属性页显示一些实时性能参数。CBaseVideoRenderer类的使用方法基本上与CBaseRenderer相同。   在DirectShow SDK基类库中,除了上述Filter和Pin类外,还有很多工具类,有了这些类的支持,我们开发Fitler或DirectShow应用程序会更加轻松。 这些类包括: CPullPin、 COutputQueue、  CSourceSeeking  、CEnumPins、 CEnumMediaTypes  、CMemAllocator 、 CMediaSample  、 CBaseReferenceClock  、CMediaType、 CBasePropertyPage  等。    

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