CBaseMediaFilter Class (Compact 2013)

Article
01/31/2017

3/26/2014

CBaseMediaFilter Class

This is an abstract base class that provides support for the IMediaFilter interface.

The CBaseMediaFilter class handles State_Stopped, State_Paused, and State_Running state transitions.

Typically, this class is used for plug-in distributors rather than filters with pins. Derive your filter classes from the CBaseFilter class (or base classes derived from this) instead of from this class.

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	Pointer to a reference clock used for synchronization. The reference count of the clock object must be incremented using AddRef. Pass NULL if no reference clock is available.
m_State	Current state of the filter, which can be State_Stopped, State_Paused, or State_Running.
m_tStart	Offset from the stream time to the reference time.

Member Functions

Member function	Description
CBaseMediaFilter	Constructs a CBaseMediaFilter object.
IsActive	Determines if the filter is active (running or paused) or stopped.

Overrideable Member Functions

Member function	Description
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 the new (paused) state.
Run	Instructs the filter to transition to the new (running) state.
SetSyncSource	Informs the filter of the reference clock it should synchronize activity with.
Stop	Instructs the filter to transition to the new (stopped) state.

Implemented INonDelegatingUnknown Methods

Method	Description
NonDelegatingQueryInterface	Passes out references to interfaces supported by CBaseFilter. To pass out pointers to interfaces supported in a derived filter class, override this.

NonDelegatingQueryInterface

Passes out references to interfaces supported by CBaseFilter.

To pass out pointers to interfaces supported in a derived filter class, override this.

Requirements

Header	dshow.h, Streams.h
Library	ole32.lib, Ole32auth.lib, Strmbase.lib, Strmiids.lib, uuid.lib

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