CBaseReferenceClock Class

Article
06/30/2006

This base class implements the IReferenceClock interface.

The CBaseReferenceClock class provides a full implementation of IReferenceClock. It uses CCritSec locking support and CAMSchedule scheduler support.

Each advise call defines a point in time when the caller wants to be notified. A periodic advise is a regular series of such events. A list of these advise requests is maintained by the reference clock. The clock calculates the delay until the first requested advise, and signals an event at the due time.

Clients are not advised through callbacks. One-shot clients have an event set, while periodic clients have a semaphore released for each event notification. A semaphore allows a client to know exactly how many events were actually triggered, because multiple time periods might elapse before the client code executes.

During class construction, a worker thread is created. This thread executes a series of Win32 WaitForSingleObject calls, waking up when a command is given to the thread or the next wake-up point is reached. The wake-up points are determined by clients making advise calls.

Protected Data Members

Member	Description
m_pSchedule	Pointer to the CAMSchedule object associated with this CBaseReferenceClock object.

Member Functions

Member function	Description
CBaseReferenceClock	Constructs a CBaseReferenceClock object.
GetSchedule	Returns the CAMSchedule pointer stored in the m_pSchedule data member.
SetTimeDelta	Adjusts the values returned from CBaseReferenceClock::GetPrivateTime by the amount specified in this member function.
TriggerThread	Triggers the advise thread's event. If you override CBaseReferenceClock::GetPrivateTime, you should either reuse or abandon this method.

Implemented IReferenceClock Methods

Method	Description
AdvisePeriodic	Requests an asynchronous periodic notification that a time has elapsed.
AdviseTime	Requests an asynchronous notification that a time has elapsed.
GetTime	Returns a reference time.
Unadvise	Removes a previously established advise link.

Overrideable Member Functions

Member function	Description
GetPrivateTime	Gets the current time from the real clock. Override this member function to implement your own clock.

Implemented INonDelegatingUnknown Methods

Method	Description
NonDelegatingQueryInterface	Returns a pointer to interfaces supported, that is, IReferenceClock.

Requirements

DirectShow applications and DirectShow filters have different include file and link library requirements. See Setting Up the Build Environment for more information.

OS Versions: Windows CE 2.12 and later. Version 2.12 requires DXPAK 1.0 or later.
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Last updated on Wednesday, April 13, 2005