IAMovieSetup接口定义
IAMovieSetup : public IUnknown
{
public:
// Adds the filter to the registry.
virtual HRESULT STDMETHODCALLTYPE Register( void) = 0;
// Removes the filter from the registry.
virtual HRESULT STDMETHODCALLTYPE Unregister( void) = 0;
};
IPersist 接口定义
IPersist : public IUnknown
{
public:
virtual HRESULT STDMETHODCALLTYPE GetClassID(
/* [out] */ CLSID *pClassID) = 0;
};
IMediaFilter 接口定义
IMediaFilter : public IPersist
{
public:
// Stops the filter.
virtual HRESULT STDMETHODCALLTYPE Stop( void) = 0;
// Pauses the filter.
virtual HRESULT STDMETHODCALLTYPE Pause( void) = 0;
// Runs the filter.
virtual HRESULT STDMETHODCALLTYPE Run(
REFERENCE_TIME tStart) = 0;
// Retrieves the state of the filter (running, stopped, or paused).
virtual HRESULT STDMETHODCALLTYPE GetState(
/* [in] */ DWORD dwMilliSecsTimeout,
/* [out] */ FILTER_STATE *State) = 0;
// Sets the reference clock for the filter or the filter graph.
virtual HRESULT STDMETHODCALLTYPE SetSyncSource(
/* [in] */ IReferenceClock *pClock) = 0;
// Retrieves the current reference clock.
virtual HRESULT STDMETHODCALLTYPE GetSyncSource(
/* [out] */ IReferenceClock **pClock) = 0;
};
IBaseFilter接口定义
IBaseFilter : public IMediaFilter
{
public:
// Enumerates the pins on this filter.
virtual HRESULT STDMETHODCALLTYPE EnumPins(
/* [out] */ IEnumPins **ppEnum) = 0;
// Retrieves the pin with the specified identifier.
virtual HRESULT STDMETHODCALLTYPE FindPin(
/* [string][in] */ LPCWSTR Id,
/* [out] */ IPin **ppPin) = 0;
// Notifies the filter that it has joined or left the filter graph.
virtual HRESULT STDMETHODCALLTYPE QueryFilterInfo(
/* [out] */ FILTER_INFO *pInfo) = 0;
// Retrieves information about the filter.
virtual HRESULT STDMETHODCALLTYPE JoinFilterGraph(
/* [in] */ IFilterGraph *pGraph,
/* [string][in] */ LPCWSTR pName) = 0;
// Retrieves a string containing vendor information.
virtual HRESULT STDMETHODCALLTYPE QueryVendorInfo(
/* [string][out] */ LPWSTR *pVendorInfo) = 0;
};
CBaseFilter类 [amfilter.h/amfilter.cpp]
CBaseFilter类的的具体实现伪代码
派生自 CUnknown, IBaseFilter, IAMovieSetup
友元类： friend class CBasePin;
成员变量部分：
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
其中，m_pLock必须通过Constructor赋值。其余指针初始化为NULL。
继承的接口函数实现
IPersist接口：
STDMETHODIMP GetClassID(CLSID *pClsID);{ m_clsid }
IAMovieSetup接口：
STDMETHODIMP Register(); // ask filter to register itself
{
// 通过调用virtual函数GetSetupData得到数据，如果为空返回S_FALSE
// 生成IFilterMapper接口，调用AMovieSetupRegisterFilter完成注册
}
STDMETHODIMP Unregister(); // and unregister itself
IMediaFilter接口：
STDMETHODIMP GetState(DWORD dwMSecs, FILTER_STATE *State);
{ m_State }
STDMETHODIMP SetSyncSource(IReferenceClock *pClock);
{ pClock->AddRef, m_pClock->Release, m_pClock = pClock;}
STDMETHODIMP GetSyncSource(IReferenceClock **pClock);
{ m_pClock->AddRef, *pCLock = m_pClock; }
// override Stop and Pause so we can activate the pins.
STDMETHODIMP Stop();
{
// 如果当前状态m_State不是State_Stopped，则遍历每个连接的Pin，调用Pin的Inactive
// 如果所有的调用均成功，设置m_State为State_Stopped.
}
STDMETHODIMP Pause();
{
// 如果当前状态m_State是State_Stopped，则遍历每个连接的Pin，调用Pin的Active
// 如果所有调用均成功，设置m_State为State_Paused.
}
// 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);
{
// 首先记住Stream的开始时间 m_tStart = tStart;
// 如果当前状态不是State_Running，则遍历每个连接的Pin，调用Pin的Run。
// 如果所有调用均成功，设置m_State为State_Running.
}
IBaseFilter接口：
// pin enumerator
STDMETHODIMP EnumPins(IEnumPins ** ppEnum);
{
// 通过Helper Class CEnumPins来完成 *ppEnum = new CEnumPins(this,
}
// default behaviour of FindPin assumes pin ids are their names
STDMETHODIMP FindPin(LPCWSTR Id, IPin ** ppPin);
{
// 遍历每个Pin，比较名称。如果找到，则对该Pin AddRef后返回。
}
STDMETHODIMP QueryFilterInfo(FILTER_INFO * pInfo);{ 填充FILTER_INFO }
STDMETHODIMP JoinFilterGraph(IFilterGraph * pGraph, LPCWSTR pName);
{
// 简单的复制m_pGraph和m_pSink(如果输入的pGraph支持IMediaEventSink)，但不对其AddRef
// 将输入的pName复制到m_pName
}
// return a Vendor information string. Optional - may return E_NOTIMPL.
// memory returned should be freed using CoTaskMemFree
STDMETHODIMP QueryVendorInfo(LPWSTR* pVendorInfo);{ E_NOTIMPL }
新增加的virtual函数
// return the current stream time - ie find out what stream time should be appearing now
virtual HRESULT StreamTime(CRefTime& rtStream);
{
// 首先得到当前Clock的时间 m_pClock->GetTime ((REFERENCE_TIME*)&rtStream)
// 然后矫正偏移 rsStream -= m_tStart
}
// find out the current pin version (used by enumerators)
virtual LONG GetPinVersion();{m_PinVersion }
// you need to supply these to access the pins from the enumerator
virtual int GetPinCount() PURE;
virtual CBasePin *GetPin(int n) PURE;
// (override to return filters setup data)
virtual LPAMOVIESETUP_FILTER GetSetupData(){ return NULL; }
其他一些相关函数
// 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);
{
// 如果m_pSink不为空，则处理消息pSink->Notify(EventCode, EventParam1, EventParam2);
// 否则返回E_NOTIMPL
}
// 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);
{
// 如果m_pGraph不为空，则通过IFilterGraph/IFilterGraph2接口调用Reconnect/ReconnectEx
// 否则返回E_NOINTERFACE
}
学习（四）将侧重于一些Helper Class的实现和CSource的分析。
