CBaseRenderer Class

Microsoft DirectShow 9.0

CBaseRenderer Class

The CBaseRenderer class is a base class for implementing renderer filters. It supports one input pin, implemented by the CRendererInputPin class. To use this class, declare a derived class that inherits CBaseRenderer. At a minimum, the derived class must implement the following methods, which are declared as pure virtual in the base class:

• CBaseRenderer::CheckMediaType: Accepts or rejects proposed media types. The filter calls this method during the pin connection process.
• CBaseRenderer::DoRenderSample: Renders a sample. The filter calls this method for every sample that it receives while running.

The base class handles state changes and synchronization issues. It also schedules samples for rendering, although it does not implement any quality-control measures. The base class also declares several "handler" methods. These are methods that the filter calls at specific points in the streaming process. They do nothing in the base class, but the derived class can override them. In the table that follows, they are listed under the heading Public Methods: Handlers.

The CBaseRenderer::OnReceiveFirstSample handler deserves special mention. The filter calls this method if it receives a sample while the filter is paused. That can occur if the graph switches from stopped to paused, or if the graph is seeked while paused. Video renderers typically use the sample to display a still frame. When the filter switches from paused to running, it sends the same sample to the CBaseRenderer::DoRenderSample method, as the first sample in the stream.

The CBaseRenderer class exposes the IMediaSeeking and IMediaPosition interfaces through the CRendererPosPassThru object. It passes all seek requests to the next filter upstream.

Scheduling

When the upstream filter calls the input pin's IMemInputPin::Receive method to deliver a sample, the pin passes this call to the filter's CBaseRenderer::Receive method. The filter either drops the sample, renders it immediately, or schedules it for rendering.

If the sample has no time stamps, or if no reference clock is available, the filter renders the sample immediately. Otherwise, the filter calls the CBaseRenderer::ShouldDrawSampleNow method to determine what to do. By default, the sample is scheduled based on its time stamps. The derived class can override ShouldDrawSampleNow to support quality control.

To schedule a sample, the filter calls the IReferenceClock::AdviseTime method, which creates an advise request. The Receive method then blocks until the scheduled time, or until the filter changes state. Blocking prevents the upstream filter from delivering more samples until the current sample is rendered.

When the upstream filter calls the IPin::EndOfStream method to signal the end of the stream, the filter sends an EC_COMPLETE event to the filter graph manager. The filter waits for the current sample's stop time before sending the event.

Requirements

**  Header:** Declared in Renbase.h; include Streams.h.

**  Library:** Use Strmbase.lib (retail builds) or Strmbasd.lib (debug builds).

Protected Member Variables
m_bAbort	Flag that indicates whether to stop rendering and reject further samples.
m_bEOS	Flag that indicates whether end-of-stream was reached.
m_bEOSDelivered	Flag that indicates whether the filter has posted the EC_COMPLETE event.
m_bInReceive	Flag that indicates whether the filter is processing a Receive call.
m_bRepaintStatus	Flag that enables or disables repaint events.
m_bStreaming	Flag that indicates whether the filter is streaming data.
m_dwAdvise	Identifier of the timer event that schedules rendering.
m_EndOfStreamTimer	Timer-event identifier, for scheduling EC_COMPLETE notifications.
m_evComplete	Event that is signaled when a state transition is complete.
m_InterfaceLock	Filter-state lock.
m_ObjectCreationLock	Lock to protect the creation of objects inside the filter.
m_pInputPin	Pointer to the filter's input pin.
m_pMediaSample	Pointer to the current media sample.
m_pPosition	Helper object to pass seek commands upstream.
m_pQSink	Pointer to the object that receives quality-control messages.
m_RendererLock	Streaming lock.
m_RenderEvent	Event used to schedule rendering.
m_SignalTime	Stop time on the current sample.
m_ThreadSignal	Event used to release the streaming thread.
Public Methods
CancelNotification	Cancels the timer event that schedules rendering. Virtual.
CBaseRenderer	Constructor method.
~CBaseRenderer	Destructor method.
GetMediaPositionInterface	Retrieves the filter's IMediaPosition and IMediaSeeking interface pointers. Virtual.
GetPin	Retrieves a pin. Virtual.
GetPinCount	Retrieves the number of pins. Virtual.
GetSampleTimes	Retrieves the time stamps from a sample. Virtual.
OnDisplayChange	Posts an EC_DISPLAY_CHANGED event to the filter graph manager.
PrepareReceive	Prepares to render a sample. Virtual.
Receive	Receives the next media sample in the stream. Virtual.
Render	Renders a sample. Virtual.
ScheduleSample	Schedules a sample for rendering. Virtual.
SendNotifyWindow	Notifies the upstream filter of the video window handle.
SendRepaint	Sends a repaint event to the filter graph manager.
SetMediaType	Called when the pin's media type is set. Virtual.
SignalTimerFired	Clears the timer identifier used to schedule rendering.
SourceThreadCanWait	Holds or releases the streaming thread. Virtual.
WaitForReceiveToComplete	Waits for the CBaseRenderer::Receive method to complete.
WaitForRenderTime	Waits for the current sample's presentation time. Virtual.
Public Methods: Accessor Methods
ClearPendingSample	Releases the current sample. Virtual.
GetCurrentSample	Retrieves the current sample. Virtual.
GetRealState	Retrieves the filter state.
GetRenderEvent	Retrieves the event that schedules rendering.
HaveCurrentSample	Determines whether the filter has a sample. Virtual.
IsEndOfStream	Queries whether the end-of-stream notification was received.
IsEndOfStreamDelivered	Queries whether the EC_COMPLETE event has been delivered to the filter graph manager.
IsStreaming	Queries whether the filter is streaming data.
SetAbortSignal	Sets a flag which indicates whether to stop rendering and reject further samples.
SetRepaintStatus	Enables or disables repaint events.
Public Methods: State-Change Methods
Active	Called when the state is switched to paused or running. Virtual.
BeginFlush	Begins a flush operation. Virtual.
BreakConnect	Releases the input pin from a connection. Virtual.
CheckReady	Queries whether a state transition is complete.
CompleteConnect	Completes the input pin's connection to another pin. Virtual.
CompleteStateChange	Determines whether a transition to the paused state is complete. Virtual.
EndFlush	Ends a flush operation. Virtual.
Inactive	Called when the state is switched to stopped. Virtual.
NotReady	Signals that a state transition is not yet complete.
Ready	Signals that a state transition is complete.
StartStreaming	Initiates streaming when the filter switches to a running state. Virtual.
StopStreaming	Halts streaming when the filter switches out of the running state. Virtual.
Public Methods: End-of-Stream Methods
EndOfStream	Notifies the filter that the input pin received an end-of-stream notification. Virtual.
NotifyEndOfStream	Posts an EC_COMPLETE event to the filter graph manager.
ResetEndOfStream	Resets the end-of-stream flags.
ResetEndOfStreamTimer	Cancels the timer that schedules EC_COMPLETE notifications. Virtual.
SendEndOfStream	If end-of-stream was reached, schedules an EC_COMPLETE event for the filter graph manager. Virtual.
TimerCallback	Callback method for the end-of-stream timer event.
Public Methods: Handlers
OnReceiveFirstSample	Called when the filter receives a sample while paused. Virtual.
OnRenderEnd	Called after a sample is rendered. Virtual.
OnRenderStart	Called when rendering is about to start. Virtual.
OnStartStreaming	Called when the filter begins streaming. Virtual.
OnStopStreaming	Called when the filter stops streaming. Virtual.
OnWaitEnd	Called when the filter is done waiting for a sample's presentation time. Virtual.
OnWaitStart	Called when the filter starts waiting for a sample's presentation time. Virtual.
PrepareRender	Called before the filter renders a sample. Virtual.
ShouldDrawSampleNow	Determines how a sample is scheduled for rendering. Virtual.
Pure Virtual Methods
CheckMediaType	Determines if the filter accepts a specific media type.
DoRenderSample	Renders a sample.
IMediaFilter Methods
GetState	Retrieves the filter's state (running, stopped, or paused).
Pause	Pauses the filter.
Run	Runs the filter.
Stop	Stops the filter.
IBaseFilter Methods
FindPin	Retrieves the pin with the specified identifier.