CTransformFilter Class

CTransformFilter is an abstract base class that supports a simple transform filter with a single input and a single output. It is derived from the CUnknown class, and it supports the IBaseFilter interface. Each pin, declared as Friends in this class, supports the IPin interface and uses the shared memory transport based on the IMemInputPin interface. The filter uses classes derived from the CBaseFilter class to support IBaseFilter; the CTransformInputPin input pin class is derived from the CBaseInputPin class, and the CTransformOutputPin output pin class is derived from the CBaseOutputPin class.

Note that, while most member functions in this class are designed to be overridden, the following pure virtual member functions must be overridden.

CheckInputType

CheckTransform

DecideBufferSize

GetMediaType

Transform

Protected Data Members

m_bEOSDelivered	End-of-stream delivery status flag.
m_bQualityChanged	Status flag that indicates if the stream has degraded. This is set to TRUE in CTransformFilter::Receive if the call to the derived class's Transform member function fails (CTransformFilter::Receive returns NOERROR in this case because returning S_FALSE indicates that the end-of-stream has arrived).
m_bSampleSkipped	Status flag that indicates if a frame was skipped.
m_csFilter	Critical section that protects the filter state. This critical section is held whenever the state is currently changing or might change. It is passed to the CBaseMediaFilter constructor so that the base class uses it too.
m_csReceive	Critical section that is held when processing events that occur on the receiving thread (CTransformInputPin::Receive and CTransformInputPin::EndOfStream).
m_idTransform	Identifier used for performance measurement. Available only when PERF is defined.
m_pInput	Pointer to the input pin class object.
m_pOutput	Pointer to the output pin class object.

Member Functions

CTransformFilter

Constructs a CTransformFilter object.

Overridable Member Functions

AlterQuality	Receives a quality-control notification from the output pin and provides an opportunity to alter the media stream's quality.
BeginFlush	Receives notification of entering the flushing state and passes it downstream.
BreakConnect	Informs the derived class when the connection is broken.
CheckConnect	Informs the derived class when the connection process is starting.
CheckInputType	Verifies that the input pin supports the media type and proposes the media type of the output pin (pure virtual).
CheckTransform	Verifies that the input and output pins support the media type (pure virtual).
CompleteConnect	Informs the derived class when the connection process has completed.
DecideBufferSize	Sets the number and size of buffers required for the transfer (pure virtual).
EndFlush	Receives notification of leaving the flushing state and passes it downstream.
EndOfStream	Receives an end-of-stream notification and passes it downstream.
GetMediaType	Returns one of the media types that the output pin supports (pure virtual).
GetPin	Returns the pin for the index specified.
GetPinCount	Returns the number of pins on the filter.
NewSegment	Informs the derived class that a new segment has started and delivers it downstream.
Receive	Receives the media sample, calls the CTransformFilter::Transform member function, and then delivers the media sample.
RegisterPerfId	Registers a performance measurement identifier.
SetMediaType	Informs the derived class when the media type is established for the connection.
StartStreaming	Informs the derived class that streaming is starting.
StopStreaming	Informs the derived class that streaming is ending.
Transform	Performs transform operations, reading from the input IMediaSample interface and writing the data to the output IMediaSample interface (pure virtual).

Implemented IBaseFilter Methods

FindPin	Retrieves the pin with the specified identifier.
Pause	Transitions the filter to State_Paused state if it is not in this state already, and informs the derived class.
Stop	Transitions the filter to State_Stopped state if it is not in this state already, and informs the derived class.

 Last updated on Tuesday, July 13, 2004

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