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分类: WINDOWS

2007-01-12 14:11:34

 

DirectShow 学习()CBasePin类、CBaseOutputPin类和CBaseInputPin类源代码解析

1.      IPin接口
IPin : public IUnknown
{
    public:
    //
连接两个Pin,主动连接InputPin
    virtual HRESULT STDMETHODCALLTYPE Connect(
            /* [in] */ IPin *pReceivePin,
            /* [in] */ const AM_MEDIA_TYPE *pmt) = 0;
    //
连接两个Pin,被动连接
    virtual HRESULT STDMETHODCALLTYPE ReceiveConnection(
            /* [in] */ IPin *pConnector,
            /* [in] */ const AM_MEDIA_TYPE *pmt) = 0;
    //
断开连接,只能在Stop状态下断开
    virtual HRESULT STDMETHODCALLTYPE Disconnect( void) = 0;
    //
得到连接的Pin的接口,成功返回连接的Pin被调用AddRef
    virtual HRESULT STDMETHODCALLTYPE ConnectedTo(
            /* [out] */ IPin **pPin) = 0;
    //
得到连接状态下的MediaType
    virtual HRESULT STDMETHODCALLTYPE ConnectionMediaType(
            /* [out] */ AM_MEDIA_TYPE *pmt) = 0;
    //
得到Pin的信息,填充PIN_INFO结构
    virtual HRESULT STDMETHODCALLTYPE QueryPinInfo(
            /* [out] */ PIN_INFO *pInfo) = 0;
    //
得到Pin的连接方向
    virtual HRESULT STDMETHODCALLTYPE QueryDirection(
            /* [out] */ PIN_DIRECTION *pPinDir) = 0;
    //
得到ID 其实是Pin中的name
    virtual HRESULT STDMETHODCALLTYPE QueryId(
            /* [out] */ LPWSTR *Id) = 0;
    // Determines whether the pin accepts a specified media type.
    virtual HRESULT STDMETHODCALLTYPE QueryAccept(
            /* [in] */ const AM_MEDIA_TYPE *pmt) = 0;
    // Enumerates the pin's preferred media types.
    virtual HRESULT STDMETHODCALLTYPE EnumMediaTypes(
            /* [out] */ IEnumMediaTypes **ppEnum) = 0;
    // Retrieves the pins that are connected internally to this pin (within the filter).
    virtual HRESULT STDMETHODCALLTYPE QueryInternalConnections(
            /* [out] */ IPin **apPin,
            /* [out][in] */ ULONG *nPin) = 0;
    // Notifies the pin that no additional data is expected
    virtual HRESULT STDMETHODCALLTYPE EndOfStream( void) = 0;
    // Begins / End a flush operation.
    virtual HRESULT STDMETHODCALLTYPE BeginFlush( void) = 0;
    virtual HRESULT STDMETHODCALLTYPE EndFlush( void) = 0;
    // Notifies the pin that media samples received after this call are grouped as a segment.
    virtual HRESULT STDMETHODCALLTYPE NewSegment(
            /* [in] */ REFERENCE_TIME tStart,
            /* [in] */ REFERENCE_TIME tStop,
            /* [in] */ double dRate) = 0;
};

2.      IQualityControl接口
IQualityControl : public IUnknown
{
public:
    // Notifies the recipient that a quality change is requested.
    virtual HRESULT STDMETHODCALLTYPE Notify(
        /* [in] */ IBaseFilter *pSelf,
        /* [in] */ Quality q) = 0;
    virtual HRESULT STDMETHODCALLTYPE SetSink(
        /* [in] */ IQualityControl *piqc) = 0;
};

3.      CBasePin[amfilter.h/amfilter.cpp]

o        派生自 CUnknown, IPin, IQualityControl
成员变量:
    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
   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
其中m_bRunTimeError默认为FALSEm_pQSink默认为NULLm_TypeVersion默认为1m_tStart为空,m_tStopMAX_TIMEm_bCanReconnectWhenActivem_bTryMyTypesFirst都为FALSEm_dRate1.0

o        Constructor:
    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
m_pFilterpFilter初始化,m_pLockpLock初始化,m_dirdir初始化。

o        Pin之间的链接过程[详细Code讲解见陆其明《DirectShow开发指南》第二章的讲解],通过调用IPinConnect>AgreeMediaType(CBasePinProtected函数)->TryMediaTypes(CBasePinProtected函数)->AttempConnect(CBasePinProtected函数)
其中AttempConnect函数会首先调用CheckConnect(CBasePinVirtual函数),然后调用CheckMediaType(CBasePinVirtual函数),如果MediaType接受,则调用Receive Pin上的ReceiveConnection(IPin接口函数)函数,如果成功则调用CompleteConnection(CBasePinvirtual函数),否则调用BreakConnect(CBasePin上的virtual函数)

o        CBasePin中的新增加virtual函数和解释以及虚拟代码:
virtual LONG GetMediaTypeVersion();{return m_TypeVersion;}
// switch the pin to active (paused or running) mode not an error to call this if already active,
virtual HRESULT Active(void);{return NOERROR;}
// switch the pin to inactive state - may already be inactive
virtual HRESULT Inactive(void);{ return NOERROR; }
// Notify of Run() from filter,
virtual HRESULT Run(REFERENCE_TIME tStart);{ return NOERROR; }
// check if the pin can support this specific proposed type and forma
virtual HRESULT CheckMediaType(const CMediaType *) PURE;
必须Override
// set the connection to use this format (previously agreed)
virtual HRESULT SetMediaType(const CMediaType *);{ HRESULT hr = m_mt.Set(*pmt);}
// check that the connection is ok before verifying it can be overridden eg to check what interfaces will be supported.
virtual HRESULT CheckConnect(IPin *);
{CBasePin
中只检查了Pin的方向和当前方向是否一致}
// Set and release resources required for a connection
virtual HRESULT BreakConnect();{return NOERROR;}
virtual HRESULT CompleteConnect(IPin *pReceivePin); {return NOERROR;}
// returns the preferred formats for a pin
virtual HRESULT GetMediaType(int iPosition,CMediaType *pMediaType);
必须Override

o        CBasePin实现IPin的函数
QueryAccept -
直接调用CheckMediaType,并将结果返回
EnumMediaTypes -
通过辅助类CEnumMediaTypes实现MediaTypeEnum.
NewSegment
只是简单设置参数后直接返回NOERROR
Disconnect
调用函数 DisconnectInternal
Connect/ReceiveConnection
见上面条目。
其它的简单接口函数 ConnectionMediaTypeQueryPinInfoQueryDirection等略。

o        CBasePin中未实现IPin/IQualityControl的函数
直接设置为NOERROR的部分函数:
EndOfStream
直接设置为IMPL错误码的部分函数:
QueryInternalConnections
Notify[IQualityControl
接口]
完全没有实现的部分函数:
BeginFlush
EndFlush

4.      CBaseOutputPin [amfilter.h/amfilter.cpp]

o        CBaseOutputPin具体实现伪代码
派生自 CBasePin
变量部分(均初始化为NULL)
IMemAllocator *m_pAllocator; // Memory allocator
IMemInputPin *m_pInputPin;  // interface on the downstreaminput pin

o        新增加的virtual函数:
// negotiate the allocator and its buffer size/count and other properties
// Calls
DecideBufferSize to set properties
virtual HRESULT DecideAllocator(IMemInputPin * pPin, IMemAllocator ** pAlloc);
{
//
调用 pPin->GetAllocatorRequirements. 得到Input PinProp.
//
调用 pPin->GetAllocator判断pPin是否以及存在Allocator
//
否则自己创建并初始化(InitAlloc)并调用 DecideBufferSize 来得到需要的大小
//
调用 pPin->NotifyAllocatorInput Pin得到更新的Allocator
}
// override this to set the buffer size and count. Return an error
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);
{
调用 m_pAllocator->GetBuffer(…) }
// deliver a filled-in sample to the connected input pin
// note - you need to release it after calling this. The receiving
virtual HRESULT Deliver(IMediaSample *);{ m_pInputPin->Receive(pSample); }
// override this to control the connection
virtual HRESULT InitAllocator(IMemAllocator **ppAlloc);{ CreateMemoryAllocator(ppAlloc); }
// called from elsewhere in our filter to pass EOS downstream to our connected input pin
virtual HRESULT DeliverEndOfStream(void);{ m_Connected->EndOfStream(); }
virtual HRESULT DeliverBeginFlush(void);{ m_Connected->BeginFlush(); }
virtual HRESULT DeliverEndFlush(void);{ m_Connected->EndFlush(); }
virtual HRESULT DeliverNewSegment(
                    REFERENCE_TIME tStart,
                    REFERENCE_TIME tStop,
                    double dRate);{ m_Connected->NewSegment(…);}

o        继承的virtual函数或者IPin接口函数:
// Complete connection
virtual HRESULT CompleteConnect(IPin *pReceivePin); { DecideAllocator() }
// Check connection
HRESULT CheckConnect(IPin *pPin);
{
增加检查输入Pin是否支持IMemInputPin接口,m_pInputPin在这里赋值}
// Break connection
HRESULT BreakConnect();
{
//
调用m_pAllocator->Decommit()释放m_pAllocator并置为空,
//
释放m_pInputPin并置为空
}
HRESULT Active(void);{ m_pAllocator->Commit(); }
HRESULT Inactive(void); { m_pAllocator->Decommit();}
以下三个函数直接返回E_UNEXPECTED
STDMETHODIMP EndOfStream(void);
STDMETHODIMP BeginFlush(void);
STDMETHODIMP EndFlush(void);

5.      IMemInputPin接口函数:
IMemInputPin : public IUnknown
{

     // Retrieves the memory allocator proposed by this pin.
     virtual HRESULT STDMETHODCALLTYPE GetAllocator(
         /* [out] */ IMemAllocator **ppAllocator) = 0;
     // Specifies an allocator for the connection.
    
virtual HRESULT STDMETHODCALLTYPE NotifyAllocator(
         /* [in] */ IMemAllocator *pAllocator,
         /* [in] */ BOOL bReadOnly) = 0;
     // Retrieves allocator properties that are requested by the input pin.
    
virtual HRESULT STDMETHODCALLTYPE GetAllocatorRequirements(
         /* [out] */ ALLOCATOR_PROPERTIES *pProps) = 0;
     // Receives the next media sample in the stream.
    
virtual HRESULT STDMETHODCALLTYPE Receive(
         /* [in] */ IMediaSample *pSample) = 0;
     // Receives multiple samples in the stream.
    
virtual HRESULT STDMETHODCALLTYPE ReceiveMultiple(
         /* [size_is][in] */ IMediaSample **pSamples,
         /* [in] */ long nSamples,
         /* [out] */ long *nSamplesProcessed) = 0;
     // Determines whether calls to the Recive method might block.
    
virtual HRESULT STDMETHODCALLTYPE ReceiveCanBlock( void) = 0;
}

6.      CBaseInputPin[amfilter.h/amfilter.cpp]

o        CBaseInputPin具体实现伪代码:
派生自 CBasePin, IMemInputPin
变量部分:
IMemAllocator *m_pAllocator;    // Default memory allocator
// Allocator is read only or not

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;
INonDelegationUnknown
的接口函数:
//
重写该函数是为了支持IMemInputPin接口
STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void **ppv);
具体实现函数:
HRESULT PassNotify(Quality& q);
{
//
如果m_pQSink不为空,直接调用m_pQSink->Notify(…)
//
否则查询Connect Pin上的IQualityControl借口,对其调用Notify(…)
}

o        新增的virtual函数
//  Override this for checking whether it's OK to process samples
//  Also call this from EndOfStream.
virtual HRESULT CheckStreaming();
{
分别判断IsStoppedm_bFlushingm_bRunTimeError }

o        IMemInputPin接口函数:
// return the allocator interface that this input pin
// would like the output pin to use
STDMETHODIMP GetAllocator(IMemAllocator ** ppAllocator);
{
//
如果m_pAllocator为空,则CreateMemoryAllocator
//
调用m_pAllocator->AddRef,返回m_pAllocator
}
// tell the input pin which allocator the output pin is actually going to use.
STDMETHODIMP NotifyAllocator(
                IMemAllocator * pAllocator,
                BOOL bReadOnly);
{
//
释放当前m_pAllocator,设置m_pAllocator = pAllocator
//
调用m_pAllocator->AddRef
}
// do something with this media sample
STDMETHODIMP Receive(IMediaSample *pSample);
{
//
首先调用CheckStreaming
//
得出pSample的属性,即填充成员m_SampleProps
//
如果Sample属性未发生变化(!(m_SampleProps.dwSampleFlags & AM_SAMPLE_TYPECHANGED))
// 则直接返回NOERROR,否则调用CheckMediaType检查是否接受新的MediaType,如果接受
//
返回NOERROR,否则调用EndOfStream,设置RuntimeError,并通知Filter
// m_pFilter->NotifyEvent(EC_ERRORABORT,VFW_E_TYPE_NOT_ACCEPTED,0);
}
// do something with these media samples
STDMETHODIMP ReceiveMultiple (
    IMediaSample **pSamples,
    long nSamples,
    long *nSamplesProcessed);
{
//
对每个Sample分别调用Receive函数。
}
// See if Receive() blocks
STDMETHODIMP ReceiveCanBlock();
{
//
如果当前Filter上没有Output Pin,则返回S_OK
//
否则遍历当前Filter上每个Output Pin,得出它们的Connected Input Pin,判断这些
// Connected Input Pin
是否支持Block,只要有一个支持,则为S_OK
//
以上条件全不满足时,返回S_FALSE
}
// 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);{E_IMPL}

o        继承的virtual函数实现
STDMETHODIMP BeginFlush(void);
{
仅仅设置m_bFlushingTRUE.}
STDMETHODIMP EndFlush(void);
{
仅仅设置m_bFlushingFALSE,同时清除m_bRuntimeError}
HRESULT BreakConnect();
{
//
如果m_pAllocator非空,调用m_pAllocator->Decommit()
//
释放m_pAllocator->Release并置为空
}
virtual HRESULT Inactive(void);
{
//
清理m_bRunTimeErrorm_bFlushing,返回m_pAllocator->Decommit().
}
STDMETHODIMP Notify(IBaseFilter * pSender, Quality q);
{
这是IQualityControl的接口函数,CBaseInputPin只是简单报错DbgBreak说明未实现}

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