CBasePin Class (Compact 2013)

Article
01/31/2017

3/26/2014

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

CBasePin supports the IPin interface. If your pin does not supply or use the IMemInputPin interface, derive from this; otherwise, derive from the CBaseInputPin class or the CBaseOutputPin class.

The connection process is crucial to the success of creating filter graphs. The filter graph finds two filters (and subsequently two pins) to connect.

It calls the IPin::Connect method on the output pin (and it can call Connect on the input pin at the same time). The output pin then calls the virtual pin member function CBasePin::CheckConnect.

Derived classes should override this member function to use QueryInterface to return any interfaces required.

The base class implementation of CheckConnect queries the IMemInputPin interface to establish the default transport protocol.

After calling CheckConnect, the output pin calls CBasePin::AgreeMediaType; this is a worker member function not intended for overriding in derived classes. This gets the input pin's enumerator and calls CBasePin::TryMediaTypes with it.

TryMediaTypes is another base pin worker member function that is not intended for derivation. It cycles through each media type provided by an enumerator to determine if a connection can be made with that type.

If that process fails, AgreeMediaType retrieves the output pin's media type enumerator and calls CBasePin::GetMediaType, which cycles through the media types to agree on a connection type. If there is agreement, a media type with the input and output pins becomes the type used in the connection.

If no media type can be agreed on, the connection between the pins cannot be made. The base pin calls CBasePin::SetMediaType to broadcast the format. The m_mt base pin variable is set during this process.

The IPin interface provides a method called QueryAccept. This method allows a connected filter to query whether the pin will accept a specified media type.

The method is asynchronous so that a filter can call it at any time - even when another filter is calling it. For this reason, its implementation in any override of the base class should not lock the filter.

The base class implementation of IPin::QueryAccept calls the overridden CBasePin::CheckMediaType member function on the derived pin 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_bRunTimeError	Run-time error generated.
m_Connected	Pin that this pin is connected to.
m_dir	Direction of this pin.
m_dRate	Rate from the CBasePin::NewSegment call.
m_mt	Media type that this pin is using. This is established during the connection process.
m_pFilter	Filter that created the pin.
m_pLock	Object used for locking.
m_pQSink	Target for quality messages.
m_pName	Name of the pin.
m_tStart	Start time from the CBasePin::NewSegment call.
m_tStop	Stop time from the CBasePin::NewSegment call.
m_TypeVersion	Current media type version (see CBasePin::GetMediaTypeVersion).

Member Functions

Member function	Description
AttemptConnection	Attempts to make a connection to another pin using a specified media type.
CBasePin	Constructs a CBasePin object.
CurrentRate	Returns the segment rate set by the CBasePin::NewSegment member function.
CurrentStartTime	Returns the segment start time set by the CBasePin::NewSegment member function.
CurrentStopTime	Returns the segment stop time set by the CBasePin::NewSegment member function.
DisplayPinInfo	Displays pin information on the debugging monitor.
DisplayTypeInfo	Displays media type information on the debugging monitor.
GetConnected	Returns the pin that is connected to this pin.
IncrementTypeVersion	Adds 1 to the current media type version.
IsConnected	Determines whether the pin is connected.
IsStopped	Determines whether the filter owning this pin is in the State_Stopped state.
Name	Returns the m_pName name of the pin.

Overrideable Member Functions

Member function	Description
Active	Switches the pin to the active (running) mode.
AgreeMediaType	Agrees on the media type to be used by the pin.
BreakConnect	Adds custom code when the connection quits. This is also called when a stage in the connection process fails, so this member function should also clean up partial connection states.
CheckConnect	Adds custom code when the connection is being made. This is called at the start of the connection process.
CheckMediaType	Checks if the pin can support a specific media type.
CompleteConnect	Completes the connection.
GetMediaType	Returns the media type used by the pin.
GetMediaTypeVersion	Returns the version of the pins that were created dynamically.
Inactive	Switches the pin to the inactive (stopped) mode.
SetMediaType	Sets the m_mt data member to the established media type.
TryMediaTypes	Tries to find an acceptable media type for a connection from the list returned by a media type enumerator.

Implemented IPin Methods

Method	Description
Connect	Initiates a connection to another pin.
ConnectedTo	Returns a pointer to the connecting pin.
ConnectionMediaType	Returns the media type of this pin's connection.
Disconnect	Breaks a connection.
EndOfStream	Informs the input pin that no additional data is expected until a new run command is issued. (By default, returns S_FALSE.)
EnumMediaTypes	Returns an enumerator for this pin's preferred media types.
NewSegment	Specifies that samples following this call are grouped as a segment with a given start time, stop time, and rate.
QueryAccept	Determines whether this pin accepts the media type.
QueryDirection	Retrieves the pin direction of the pin.
QueryId	Retrieves an identifier for the pin.
QueryInternalConnections	Returns an array of the pins that this pin connects to internally.
QueryPinInfo	Retrieves information about the pin (name, owning filter, or direction).
ReceiveConnection	Called by a connecting pin to make a connection to this pin. Usually this does not need to be overridden, because the default implementation calls CBasePin::CheckConnect, CBasePin::CheckMediaType, and CBasePin::BreakConnect.
Run	Notifies the pin that the filter has changed state from paused to running.

Implemented IQualityControl Methods

Method	Description
Notify	Notifies the recipient that a quality change is requested.
SetSink	Sets the IQualityControl object that will receive quality messages.

Implemented INonDelegatingUnknown Methods

Method	Description
NonDelegatingAddRef	Increments the owning filter's reference count.
NonDelegatingQueryInterface	Retrieves CBasePin interfaces. To pass out pointers to interfaces added by the derived pin class, override this member function.
NonDelegatingRelease	Decrements the owning filter's reference count.

NonDelegatingAddRef

Increments the owning filter's reference count.

NonDelegatingQueryInterface

Retrieves CBasePin interfaces.

To pass out pointers to interfaces added by the derived pin class, override this member function.

NonDelegatingRelease

Decrements the owning filter's reference count.

Requirements

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