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CBaseFilter Class (Compact 2013)

3/26/2014

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This is an abstract base class from which all filters are derived.

It supports the Component Object Model (COM) IBaseFilter interface and is derived from the CUnknown class. This class supports the enumeration of pins by calling the pure virtual member functions CBaseFilter::GetPin and GetPinCount. These member functions must be overridden by any derived class.

The CBaseFilter class assumes that all the filter's pins are derived from the CBasePin class. CBaseFilter::GetPin must return a pointer to CBasePin.

All member functions in this class that return HRESULT and accept a pointer as a parameter return E_POINTER when passed a null pointer.

Protected Data Members

Member

Description

m_clsid

Class identifier (CLSID) used for serialization using IPersist.

m_pClock

Filter graph's reference clock.

m_pGraph

Pointer to a graph to which this filter belongs.

m_PinVersion

Current version of the pins used on the filter.

m_pLock

Pointer to the critical section used for locking.

m_pName

Filter name.

m_pSink

Pointer to the IMediaEventSink interface on the filter graph manager.

m_State

Current state: running or paused.

m_tStart

Offset from the stream time to the reference time.

Member Functions

Member function

Description

CBaseFilter

Constructs a CBaseFilter object.

GetFilterGraph

Returns the filter graph associated with the filter. This is used in the implementation of CEnumPins.

IncrementPinVersion

Adds 1 to the pin version stored in m_PinVersion.

IsActive

Determines if the filter is currently active (running or paused) or stopped.

NotifyEvent

Sends an event notification to the filter graph.

ReconnectPin

Requests pin for a reconnect.

Overrideable Member Functions

Member function

Description

GetPin

Returns a pointer to the requested pin.

GetPinCount

Returns the number of pins currently available on this object.

GetPinVersion

Returns the current version of the base filter for comparison with the version with which the pin was initialized.

This member function can be overridden if pins are being created dynamically.

GetSetupData

Retrieves the registration data associated with the filter.

StreamTime

Returns the current stream time.

Implemented IPersist Methods

Method

Description

GetClassID

Returns the class identifier of this filter.

Implemented IMediaFilter Methods

Method

Description

GetState

Retrieves the current state of the filter.

GetSyncSource

Retrieves the current reference clock in use by this filter.

Pause

Instructs the filter to transition to State_Paused state.

Run

Instructs the filter to transition to State_Running state.

Passes a time value to synchronize independent streams.

SetSyncSource

Informs the filter of the reference clock with which it should synchronize activity.

Stop

Instructs the filter to transition to the State_Stopped state.

Implemented IBaseFilter Methods

Method

Description

EnumPins

Provides an enumerator for this pin's preferred media types (implemented by this class).

FindPin

Retrieves the pin with the specified identifier.

JoinFilterGraph

Notifies a filter that it has joined a filter graph (implemented by this class).

QueryFilterInfo

Gets information about the specified filter (implemented by this class).

QueryVendorInfo

Retrieves optional information supplied by a vendor for the specified filter.

Implemented IAMovieSetup Methods

Method

Description

Register

Adds the filter to the registry.

Unregister

Removes the filter from the registry.

Implemented INonDelegatingUnknown Methods

Method

Description

NonDelegatingQueryInterface

Passes out pointers to any interfaces added to the derived filter class.

Requirements

Header

dshow.h,
Streams.h

Library

ole32.lib,
Ole32auth.lib,
Strmbase.lib,
Strmiids.lib,
uuid.lib

See Also

Reference

DirectShow Classes