Re: Sending UDP data at a fixed rate

From:
PaulH <paul.heil@gmail.com>
Newsgroups:
microsoft.public.vc.language
Date:
Fri, 29 Feb 2008 15:20:47 -0800 (PST)
Message-ID:
<130662bf-8679-4e37-8e12-04d99e1cd8ef@u10g2000prn.googlegroups.com>
On Feb 29, 4:48 pm, "Mark Salsbery [MVP]"
<MarkSalsbery[MVP]@newsgroup.nospam> wrote:

I'm curious....how are you measuring the inter-datagram delay? Is there=

ever a chance sendto() is blocking?

In my multimedia communication software, I get very steady inter-datagram
timing on XP and Vista, but on 2000 it gets chunky (datagrams sent in
bunches).
This drove me nuts for a while trying to implement jitter buffers for
multimedia streaming :)

Mark

--
Mark Salsbery
Microsoft MVP - Visual C++

"PaulH" <paul.h...@gmail.com> wrote in message

news:44696dd8-0b37-4fe2-9884-abb7a9134e0e@p73g2000hsd.googlegroups.com...

On Feb 29, 2:22 pm, "Mark Salsbery [MVP]"
<MarkSalsbery[MVP]@newsgroup.nospam> wrote:

"PaulH" <paul.h...@gmail.com> wrote in message

news:e6f36848-5086-4e6a-9933-902a307b418c@i12g2000prf.googlegroups.com..=

..

I have a program that I want to use to send UDP data frames at a fixe=

d

rate. Right now, at 25ms between frames about 1 in 10 is delayed by a=

few ms. I've used other programs that manage to get this kind of
success at 10ms between frames.

I'm using a multimedia timer (see below) to get my current level of
accuracy. What can I do to improve things?

Thanks,
PaulH

int delay = 25; //25 ms between frames
HANDLE hSendNextFrame = CreateEvent( NULL, FALSE, FALSE, NULL );


Do you call timeBeginPeriod() before creating the periodic timer?

Something like:

TIMECAPS tc;
if (::timeGetDevCaps(&tc, sizeof(TIMECAPS)) == TIMERR_NOERROR)
{
// Try for 1ms resolution - accept best
UINT TimerRes = min(max(tc.wPeriodMin, 1), tc.wPeriodMax);
::timeBeginPeriod(TimerRes);

Mark

--
Mark Salsbery
Microsoft MVP - Visual C++

MMRESULT mmNextFrameTimer = timeSetEvent( delay,
1,
reinterpret_cast<
LPTIMECALLBACK >( hSendNextFrame ),
NULL,
TIME_PERIODIC |
TIME_CALLBACK_EVENT_SET );

while( TRUE ) {
if( sendto( address, data ) < 0 ) {
//error condition
}

::WaitForSingleObject( hSendNextFrame, delay + 100 );
}

timeKillEvent( mmNextFrameTime );
CloseHandle( hSendNextFrame );


Good thought. But, timeSetEvent() already calls timeBeginPeriod() to
set the accuracy.
http://blogs.msdn.com/larryosterman/archive/2005/09/08/462477.aspx

I tried it anyway to see if it helped. It did not.

-PaulH


I'm using Wireshark for that. (on a seperate PC)

-PaulH

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