SetTimer vs Sleep

[oex]

Thank you Michael and JJ both interesting posts.... I have run the test app with the following results:

Sleep(1) delay  = 1.990 ms
Sleep(10) delay = 10.946 ms

[Siekmanski]

You can try using the GetTime and the one-shot timer AdviseTime ( I'm using the one from DirectSound to fill the soundbuffer without the use of notifications  :bg)

Let the timer run in its own thread with high priority using CreateThread and SetThreadPriority
And create a timer-event with CreateEvent


GetTime delivers the time in the type REFERENCE_TIME

   coinvoke   g_pDS_Timer,IReferenceClock,GetTime,addr RefClockTime ; receives the current time, in 100-nanosecond units.

   coinvoke   g_pDS_Timer,IReferenceClock,AdviseTime,RefClockTime,StreamTime,DS_TimerEvent,addr pdwAdviseCookie


http://msdn.microsoft.com/ja-jp/library/cc369473(v=MSDN.10).aspx

[oex]

This is great guys.... So many ways to do nothing :lol

[jj2007]

One more, using timeSetEvent. Resolution is one millisecond, and CPU usage does not increase. The attached executable needs SSE2 (sorry Michael :()

Code Select Expand

include \masm32\MasmBasic\MasmBasic.inc ; http://www.masm32.com/board/index.php?topic=12460
uselib winmm
CbTimer PROTO:DWORD,:DWORD,:DWORD,:DWORD,:DWORD

.data?
Counter SDWORD ?
Ticks dd ?
TimerID dd ?

Init

Open "O", #1, "TimerTest.txt"
mov Counter, 10000 ; will run 10 seconds, enough to check CPU usage
mov Ticks, Timer()
mov TimerID, rv(timeSetEvent, 1, 1, CbTimer, 0, TIME_PERIODIC or TIME_KILL_SYNCHRONOUS)
.if eax
.Repeat
invoke Sleep, 100
.Until Counter<=0
.endif
Close

Inkey Str$("\n\nYour puter has run %3f hours since the last boot, give it a break!", Timer()/3600000)
Exit

CbTimer proc ID:DWORD, uMsg:DWORD, dwUser:DWORD, dw1:DWORD, dw2:DWORD
  dec Counter
  .if Sign?
invoke timeKillEvent, TimerID
  .else
mov ecx, Timer()
sub ecx, Ticks
Print #1, Str$(Counter), Tb$, Str$(ecx), CrLf$
  .endif
  ret
CbTimer endp
end start


[clive]

The authors are probably wrong about the 100ns.

The resolution of the time base used by Microsoft (FILETIME) is 100 ns, the granularity of the updates are going to be significantly higher. With all these timer constructs, the event occurs when the system identifies that all the delay has been exhausted, not at the time requested. With the granularity, you don't even know the time you actually started with any real precision. What you really need is a free running hardware counter that is clocking at a known/stable frequency, ideally disciplined with GPS, NTP or IEEE-1588.

ie

CurrentTime += 5000; (CurrentTime - StartTime) >= TimeOut;

StartTime could also be set at tick 0 .. 4999

or

CurrentTime += 5000; (CurrentTime - TargetTime) >= 0;

The specific trick with video frames is not to let time slip/drift accumulate. You get the time at the beginning of playback, and increment the target time at the frame rate, and achieve addition discipline from the audio (known/stable frequency, but probably *not* synchronous to your system timebase).

The time of any specific Sleep(), or whatever method, should be irrelevant.

[jj2007]

Clive,
My previous posts uses the MM timer, which has the required features for a more or less stable 1 ms resolution. See sample output below. The left column is the counter for Print #1, the second one is the elapsed GetTickCount since launching the timer.

Code Select Expand

9999 0
9998 0
9997 0
9996 0
9995 0
9994 0
9993 0
9992 0
9991 0
9990 0
9989 0
9988 0
9987 0
9986 15
9985 15
9984 15
9983 15
9982 15
9981 15
9980 15
9979 15
...
18 9968
17 9984
16 9984
15 9984
14 9984
13 9984
12 9984
11 9984
10 9984
9 9984
8 9984
7 9984
6 9984
5 9984
4 9984
3 9984
2 9984
1 10000
0 10000


[oex]

These messages have already illuminated a glaringly obvious mistake in my code.... I was using GetTickCount in conjunction with Sleep to check if I was into the next time frame :/.... Thanks guys for your help you have saved me milliseconds!!!! :bg

[joemc]

you may wish to check out VideoLAN's VLC player.  it is open source if you wish to see how they implement video.

[oex]

E^Cube suggested NtDelayExecution (also 100ns) on another post, thought I might add a note this has been very useful info for me