170 lines
6.8 KiB
C++
170 lines
6.8 KiB
C++
//------------------------------------------------------------------------------
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// File: RefClock.h
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//
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// Desc: DirectShow base classes - defines the IReferenceClock interface.
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//
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// Copyright (c) 1992-2001 Microsoft Corporation. All rights reserved.
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//------------------------------------------------------------------------------
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#ifndef __BASEREFCLOCK__
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#define __BASEREFCLOCK__
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#include <Schedule.h>
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const UINT RESOLUTION = 1; /* High resolution timer */
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const INT ADVISE_CACHE = 4; /* Default cache size */
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const LONGLONG MAX_TIME = 0x7FFFFFFFFFFFFFFF; /* Maximum LONGLONG value */
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inline LONGLONG WINAPI ConvertToMilliseconds(const REFERENCE_TIME& RT)
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{
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/* This converts an arbitrary value representing a reference time
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into a MILLISECONDS value for use in subsequent system calls */
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return (RT / (UNITS / MILLISECONDS));
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}
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/* This class hierarchy will support an IReferenceClock interface so
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that an audio card (or other externally driven clock) can update the
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system wide clock that everyone uses.
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The interface will be pretty thin with probably just one update method
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This interface has not yet been defined.
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*/
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/* This abstract base class implements the IReferenceClock
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* interface. Classes that actually provide clock signals (from
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* whatever source) have to be derived from this class.
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*
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* The abstract class provides implementations for:
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* CUnknown support
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* locking support (CCritSec)
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* client advise code (creates a thread)
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*
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* Question: what can we do about quality? Change the timer
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* resolution to lower the system load? Up the priority of the
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* timer thread to force more responsive signals?
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*
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* During class construction we create a worker thread that is destroyed during
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* destuction. This thread executes a series of WaitForSingleObject calls,
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* waking up when a command is given to the thread or the next wake up point
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* is reached. The wakeup points are determined by clients making Advise
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* calls.
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*
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* Each advise call defines a point in time when they wish to be notified. A
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* periodic advise is a series of these such events. We maintain a list of
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* advise links and calculate when the nearest event notification is due for.
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* We then call WaitForSingleObject with a timeout equal to this time. The
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* handle we wait on is used by the class to signal that something has changed
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* and that we must reschedule the next event. This typically happens when
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* someone comes in and asks for an advise link while we are waiting for an
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* event to timeout.
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*
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* While we are modifying the list of advise requests we
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* are protected from interference through a critical section. Clients are NOT
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* advised through callbacks. One shot clients have an event set, while
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* periodic clients have a semaphore released for each event notification. A
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* semaphore allows a client to be kept up to date with the number of events
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* actually triggered and be assured that they can't miss multiple events being
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* set.
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*
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* Keeping track of advises is taken care of by the CAMSchedule class.
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*/
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class CBaseReferenceClock
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: public CUnknown, public IReferenceClock, public CCritSec
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{
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protected:
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virtual ~CBaseReferenceClock(); // Don't let me be created on the stack!
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public:
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CBaseReferenceClock(TCHAR *pName, LPUNKNOWN pUnk, HRESULT *phr, CAMSchedule * pSched = 0 );
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STDMETHODIMP NonDelegatingQueryInterface(REFIID riid,void ** ppv);
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DECLARE_IUNKNOWN
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/* IReferenceClock methods */
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// Derived classes must implement GetPrivateTime(). All our GetTime
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// does is call GetPrivateTime and then check so that time does not
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// go backwards. A return code of S_FALSE implies that the internal
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// clock has gone backwards and GetTime time has halted until internal
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// time has caught up. (Don't know if this will be much use to folk,
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// but it seems odd not to use the return code for something useful.)
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STDMETHODIMP GetTime(REFERENCE_TIME *pTime);
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// When this is called, it sets m_rtLastGotTime to the time it returns.
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/* Provide standard mechanisms for scheduling events */
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/* Ask for an async notification that a time has elapsed */
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STDMETHODIMP AdviseTime(
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REFERENCE_TIME baseTime, // base reference time
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REFERENCE_TIME streamTime, // stream offset time
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HEVENT hEvent, // advise via this event
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DWORD_PTR *pdwAdviseCookie // where your cookie goes
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);
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/* Ask for an asynchronous periodic notification that a time has elapsed */
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STDMETHODIMP AdvisePeriodic(
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REFERENCE_TIME StartTime, // starting at this time
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REFERENCE_TIME PeriodTime, // time between notifications
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HSEMAPHORE hSemaphore, // advise via a semaphore
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DWORD_PTR *pdwAdviseCookie // where your cookie goes
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);
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/* Cancel a request for notification(s) - if the notification was
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* a one shot timer then this function doesn't need to be called
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* as the advise is automatically cancelled, however it does no
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* harm to explicitly cancel a one-shot advise. It is REQUIRED that
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* clients call Unadvise to clear a Periodic advise setting.
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*/
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STDMETHODIMP Unadvise(DWORD_PTR dwAdviseCookie);
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/* Methods for the benefit of derived classes or outer objects */
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// GetPrivateTime() is the REAL clock. GetTime is just a cover for
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// it. Derived classes will probably override this method but not
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// GetTime() itself.
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// The important point about GetPrivateTime() is it's allowed to go
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// backwards. Our GetTime() will keep returning the LastGotTime
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// until GetPrivateTime() catches up.
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virtual REFERENCE_TIME GetPrivateTime();
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/* Provide a method for correcting drift */
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STDMETHODIMP SetTimeDelta( const REFERENCE_TIME& TimeDelta );
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CAMSchedule * GetSchedule() const { return m_pSchedule; }
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private:
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REFERENCE_TIME m_rtPrivateTime; // Current best estimate of time
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DWORD m_dwPrevSystemTime; // Last vaule we got from timeGetTime
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REFERENCE_TIME m_rtLastGotTime; // Last time returned by GetTime
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REFERENCE_TIME m_rtNextAdvise; // Time of next advise
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UINT m_TimerResolution;
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#ifdef PERF
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int m_idGetSystemTime;
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#endif
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// Thread stuff
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public:
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void TriggerThread() // Wakes thread up. Need to do this if
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{ // time to next advise needs reevaluating.
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EXECUTE_ASSERT(SetEvent(m_pSchedule->GetEvent()));
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}
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private:
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BOOL m_bAbort; // Flag used for thread shutdown
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HANDLE m_hThread; // Thread handle
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HRESULT AdviseThread(); // Method in which the advise thread runs
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static DWORD __stdcall AdviseThreadFunction(LPVOID); // Function used to get there
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protected:
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CAMSchedule * const m_pSchedule;
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};
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#endif
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