// from RFC 1889, Real Time Protocol (RTP) 
            // J = J + ( | D(i-1,i) | - J ) / 16 
            transit = TimeDifference( packet->packetTime, packet->sentTime );
            if ( data->lastTransit != 0.0 ) {
                deltaTransit = transit - data->lastTransit;
                if ( deltaTransit < 0.0 ) {
                    deltaTransit = -deltaTransit;
                }
                stats->jitter += (deltaTransit - stats->jitter) / (16.0);
            }
            data->lastTransit = transit;