Re: threads and their time slots. - C / C++ / MFC Discussion Boards

Stuart Dootson3-Jul-09 0:31

3-Jul-09 0:31

Let me get my traditional admonition about Windows + real-time behaviour out of the way first - Windows is not anywhere near being a real-time OS, there's too much stuff going on, it has high interrupt latency etc etc. Ha, that's better.

Now - the one thing that may improve your situation is to increase the priority of your sending thread. Alternatively, you could use a different strategy - use a waitable timer[^], with a completion routine that sends the packet. Put the thread into an alertable wait state when you set the timer and the completion routine should get called by the timer.

The advantage of doing this is that the more your code is running, the more Windows will give a dynamic priority boost to other, similarly prioritised threads. If your code sleeps, that won't happen, and also, your system as a whole will be slightly more responsive.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: threads and their time slots. [modified]

Souldrift3-Jul-09 1:17

Souldrift

3-Jul-09 1:17

Thanks for the idea. I tried it (very exitedly). But I´m running into the same problem.
My new code is:

int RTPEngine::SendRTPPacket( BYTE* data, int size )
{
	if( data && size > 0 && m_pHeader )
	{
		m_pLogger->Out(Logger::DEBUG, "RTPEngine: Sending data package with size %d (excluding header).\n", size);

		BYTE* packet = new BYTE[size+12];
		BYTE* headerBytes = m_pHeader->GetInc();

		for( int i = 0; i < 12; i++ )
		{
			packet[i] = headerBytes[i];
		}
		for( int i = 0; i < size; i++ )
		{
			packet[i+12] = data[i];
		}

		double now = 0.0; // milliseconds
		if( m_dPacketSendTime != 0.0 )
		{
			now = ((double) clock() / CLK_TCK) * 1000; // milliseconds
			m_pLogger->Out( Logger::DEBUG, "RTPEngine: Time now = %f.\n", now );
			double dueMS = m_dPacketSendTime-now; // relative time to wait in ms
			if( dueMS > 0 )
			{
				HANDLE hTimer = 0;
				LARGE_INTEGER liDueTime;
				hTimer = ::CreateWaitableTimer(0, TRUE, L"WaitableTimer");
				liDueTime.QuadPart = -((int)dueMS * 10000); // relative waitin time converted to '100-nanoseconds'
				SetWaitableTimer(hTimer, &liDueTime, 0, NULL, NULL, FALSE);
				::WaitForSingleObject(hTimer, INFINITE);
			}
		}

		now = ((double) clock() / CLK_TCK) * 1000;
		int rc=sendto(m_oUDPSocket,(char*)packet,size+12,0,(SOCKADDR*)&m_oUDPAddress,sizeof(SOCKADDR_IN));

		m_pLogger->Out( Logger::DEBUG, "RTPEngine: Packet sent at = %f.\n", now );

		m_dPacketSendTime = ((double) clock() / CLK_TCK) * 1000; // milliseconds
		m_dPacketSendTime += (m_dPacketLengthMillis*(1.0 - m_dRTPOverlap));
		m_pLogger->Out( Logger::DEBUG, "RTPEngine: Next send time = %f.\n", m_dPacketSendTime );

		return size;
	}
	else
		return 0;
}

I´m at a loss ...

Souldrift

Edit:

Actually I just found that this doesn´t work as expected. The output is:

RTPEngine: Next send time = 3009.
RTPEngine: Sending data package with size 480 (excluding header).
RTPEngine: Time now = 3000.
RTPEngine: Packet sent at = 3000.
RTPEngine: Next send time = 3009.
RTPEngine: Sending data package with size 480 (excluding header).
RTPEngine: Time now = 3000.
RTPEngine: Packet sent at = 3000.
RTPEngine: Next send time = 3009.
RTPEngine: Sending data package with size 480 (excluding header).
RTPEngine: Time now = 3000.
RTPEngine: Packet sent at = 3000.

It doesn´t wait at all ??

modified on Friday, July 3, 2009 7:34 AM

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