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1 //------------------------------------------------------------------------------
2 // File: RefClock.h
3 //
4 // Desc: DirectShow base classes - defines the IReferenceClock interface.
5 //
6 // Copyright (c) 1992-2002 Microsoft Corporation. All rights reserved.
7 //------------------------------------------------------------------------------
10 #ifndef __BASEREFCLOCK__
11 #define __BASEREFCLOCK__
13 #include "dsschedule.h"
15 const UINT RESOLUTION = 1; /* High resolution timer */
16 const INT ADVISE_CACHE = 4; /* Default cache size */
17 const LONGLONG MAX_TIME = 0x7FFFFFFFFFFFFFFF; /* Maximum LONGLONG value */
19 inline LONGLONG WINAPI ConvertToMilliseconds(const REFERENCE_TIME& RT)
21 /* This converts an arbitrary value representing a reference time
22 into a MILLISECONDS value for use in subsequent system calls */
24 return (RT / (UNITS / MILLISECONDS));
27 /* This class hierarchy will support an IReferenceClock interface so
28 that an audio card (or other externally driven clock) can update the
29 system wide clock that everyone uses.
31 The interface will be pretty thin with probably just one update method
32 This interface has not yet been defined.
35 /* This abstract base class implements the IReferenceClock
36 * interface. Classes that actually provide clock signals (from
37 * whatever source) have to be derived from this class.
39 * The abstract class provides implementations for:
40 * CUnknown support
41 * locking support (CCritSec)
42 * client advise code (creates a thread)
44 * Question: what can we do about quality? Change the timer
45 * resolution to lower the system load? Up the priority of the
46 * timer thread to force more responsive signals?
48 * During class construction we create a worker thread that is destroyed during
49 * destuction. This thread executes a series of WaitForSingleObject calls,
50 * waking up when a command is given to the thread or the next wake up point
51 * is reached. The wakeup points are determined by clients making Advise
52 * calls.
54 * Each advise call defines a point in time when they wish to be notified. A
55 * periodic advise is a series of these such events. We maintain a list of
56 * advise links and calculate when the nearest event notification is due for.
57 * We then call WaitForSingleObject with a timeout equal to this time. The
58 * handle we wait on is used by the class to signal that something has changed
59 * and that we must reschedule the next event. This typically happens when
60 * someone comes in and asks for an advise link while we are waiting for an
61 * event to timeout.
63 * While we are modifying the list of advise requests we
64 * are protected from interference through a critical section. Clients are NOT
65 * advised through callbacks. One shot clients have an event set, while
66 * periodic clients have a semaphore released for each event notification. A
67 * semaphore allows a client to be kept up to date with the number of events
68 * actually triggered and be assured that they can't miss multiple events being
69 * set.
71 * Keeping track of advises is taken care of by the CAMSchedule class.
74 class CBaseReferenceClock
75 : public CUnknown, public IReferenceClock, public CCritSec
77 protected:
78 virtual ~CBaseReferenceClock(); // Don't let me be created on the stack!
79 public:
80 CBaseReferenceClock(TCHAR *pName, LPUNKNOWN pUnk, HRESULT *phr, CAMSchedule * pSched = 0 );
82 STDMETHODIMP NonDelegatingQueryInterface(REFIID riid,void ** ppv);
84 DECLARE_IUNKNOWN
86 /* IReferenceClock methods */
87 // Derived classes must implement GetPrivateTime(). All our GetTime
88 // does is call GetPrivateTime and then check so that time does not
89 // go backwards. A return code of S_FALSE implies that the internal
90 // clock has gone backwards and GetTime time has halted until internal
91 // time has caught up. (Don't know if this will be much use to folk,
92 // but it seems odd not to use the return code for something useful.)
93 STDMETHODIMP GetTime(REFERENCE_TIME *pTime);
94 // When this is called, it sets m_rtLastGotTime to the time it returns.
96 /* Provide standard mechanisms for scheduling events */
98 /* Ask for an async notification that a time has elapsed */
99 STDMETHODIMP AdviseTime(
100 REFERENCE_TIME baseTime, // base reference time
101 REFERENCE_TIME streamTime, // stream offset time
102 HEVENT hEvent, // advise via this event
103 DWORD_PTR *pdwAdviseCookie // where your cookie goes
106 /* Ask for an asynchronous periodic notification that a time has elapsed */
107 STDMETHODIMP AdvisePeriodic(
108 REFERENCE_TIME StartTime, // starting at this time
109 REFERENCE_TIME PeriodTime, // time between notifications
110 HSEMAPHORE hSemaphore, // advise via a semaphore
111 DWORD_PTR *pdwAdviseCookie // where your cookie goes
114 /* Cancel a request for notification(s) - if the notification was
115 * a one shot timer then this function doesn't need to be called
116 * as the advise is automatically cancelled, however it does no
117 * harm to explicitly cancel a one-shot advise. It is REQUIRED that
118 * clients call Unadvise to clear a Periodic advise setting.
121 STDMETHODIMP Unadvise(DWORD_PTR dwAdviseCookie);
123 /* Methods for the benefit of derived classes or outer objects */
125 // GetPrivateTime() is the REAL clock. GetTime is just a cover for
126 // it. Derived classes will probably override this method but not
127 // GetTime() itself.
128 // The important point about GetPrivateTime() is it's allowed to go
129 // backwards. Our GetTime() will keep returning the LastGotTime
130 // until GetPrivateTime() catches up.
131 virtual REFERENCE_TIME GetPrivateTime();
133 /* Provide a method for correcting drift */
134 STDMETHODIMP SetTimeDelta( const REFERENCE_TIME& TimeDelta );
136 CAMSchedule * GetSchedule() const { return m_pSchedule; }
138 private:
139 REFERENCE_TIME m_rtPrivateTime; // Current best estimate of time
140 DWORD m_dwPrevSystemTime; // Last vaule we got from timeGetTime
141 REFERENCE_TIME m_rtLastGotTime; // Last time returned by GetTime
142 REFERENCE_TIME m_rtNextAdvise; // Time of next advise
143 UINT m_TimerResolution;
145 #ifdef PERF
146 int m_idGetSystemTime;
147 #endif
149 // Thread stuff
150 public:
151 void TriggerThread() // Wakes thread up. Need to do this if
152 { // time to next advise needs reevaluating.
153 EXECUTE_ASSERT(SetEvent(m_pSchedule->GetEvent()));
157 private:
158 BOOL m_bAbort; // Flag used for thread shutdown
159 HANDLE m_hThread; // Thread handle
161 HRESULT AdviseThread(); // Method in which the advise thread runs
162 static DWORD __stdcall AdviseThreadFunction(LPVOID); // Function used to get there
164 protected:
165 CAMSchedule * const m_pSchedule;
168 #endif