[Live-devel] Simulation and packet loss, part three

[Antonio Tirri]

Hi,
I edited the live555 mediaserver in order to apply the Gilbert model to 
send the video packets (gilbert model.jpg)

The code is:

void MultiFramedRTPSink::sendPacketIfNecessary() {  //antonio
    static int state = 0;
    double p = 0.70;   // defining p
    double q = 0.20;   // defining q
    if (fNumFramesUsedSoFar > 0) {
      if ((state == 0) && ((double)(our_random()%10000))/10000.0 <= p) 
stato =1;
      else if((state == 1) && ((double)(our_random()%10000))/10000.0 
<=q) stato =0;
      if(stato == 0)fRTPInterface.sendPacket(fOutBuf->packet(),
fOutBuf->curPacketSize());
      ++fPacketCount;
      fTotalOctetCount += fOutBuf->curPacketSize();
      fOctetCount += fOutBuf->curPacketSize()
        - rtpHeaderSize - fSpecialHeaderSize - 
fTotalFrameSpecificHeaderSizes;

      ++fSeqNo; // for next time
}


   if (fOutBuf->haveOverflowData()
       && fOutBuf->totalBytesAvailable() > fOutBuf->totalBufferSize()/2) {
     // Efficiency hack: Reset the packet start pointer to just in front of
     // the overflow data (allowing for the RTP header and special headers),
     // so that we probably don't have to "memmove()" the overflow data
     // into place when building the next packet:
     unsigned newPacketStart = fOutBuf->curPacketSize()
       - (rtpHeaderSize + fSpecialHeaderSize + frameSpecificHeaderSize());
     fOutBuf->adjustPacketStart(newPacketStart);
   } else {
     // Normal case: Reset the packet start pointer back to the start:
     fOutBuf->resetPacketStart();
   }
   fOutBuf->resetOffset();
   fNumFramesUsedSoFar = 0;

   if (fNoFramesLeft) {
     // We're done:
     onSourceClosure(this);
   } else {
     // We have more frames left to send.  Figure out when the next frame
     // is due to start playing, then make sure that we wait this long 
before
     // sending the next packet.
     struct timeval timeNow;
     gettimeofday(&timeNow, NULL);
     int uSecondsToGo;
     if (fNextSendTime.tv_sec < timeNow.tv_sec) {
       uSecondsToGo = 0; // prevents integer underflow if too far behind
     } else {
       uSecondsToGo = (fNextSendTime.tv_sec - timeNow.tv_sec)*1000000
	+ (fNextSendTime.tv_usec - timeNow.tv_usec);
     }

     // Delay this amount of time:
     nextTask() = envir().taskScheduler().scheduleDelayedTask(uSecondsToGo,
						(TaskFunc*)sendNext, this);
   }
}


I need to implement a scrambler and a descrambler as showed in the 
modello.gif, in order to implement this technique of scrambling
(for more information: 
http://en.wikipedia.org/wiki/Scrambler_%28randomizer%29 )

How can i start this work?

Thanks,
Antonio Tirri
-------------- next part --------------
A non-text attachment was scrubbed...
Name: modello.GIF
Type: image/gif
Size: 2376 bytes
Desc: not available
Url : http://lists.live555.com/pipermail/live-devel/attachments/20070313/72f82c1f/attachment-0001.gif 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: gilbert model.jpg
Type: image/jpeg
Size: 11902 bytes
Desc: not available
Url : http://lists.live555.com/pipermail/live-devel/attachments/20070313/72f82c1f/attachment-0001.jpg