code: public long getFractionLost() {
  //		long expected = this.lastSequenceNumber - this.lastSrSequenceNumber;
  //		if (expected < 0) {
  //			expected = RTP_SEQ_MOD + expected;
  //		}
  //
  //		long fraction = 256 * (expected - this.receivedSinceSR);
  //		fraction = expected > 0 ? (fraction / expected) : 0;
  //
  //		return fraction;
  		
  		long expected = getPacketsExpected();
  		long expectedInterval = expected - this.expectedPrior;
  		this.expectedPrior = expected;
  		
  		long receivedInterval = this.receivedPackets - this.receivedPrior;
  		this.receivedPrior = this.receivedPackets;
  		
  		long lostInterval = expectedInterval - receivedInterval;
  		if(expectedInterval == 0 || lostInterval <= 0) {
  			return 0;
  		}
  		return (lostInterval << 8) / expectedInterval;
  	}
docs: Gets the fraction of RTP data packets from this source that were lost
  since the previous SR or RR packet was sent, expressed as a fixed point
  number with the binary point at the left edge of the field. (That is
  equivalent to taking the integer part after multiplying the loss fraction
  by 256.)
  
  @return The fraction of lost packets