interarrival jitter: 32 bits
An estimate of the statistical variance of the RTP data packet
interarrival time, measured in timestamp units and expressed as an
unsigned integer. The interarrival jitter J is defined to be the
mean deviation (smoothed absolute value) of the difference D in
packet spacing at the receiver compared to the sender for a pair
of packets. As shown in the equation below, this is equivalent to
the difference in the "relative transit time" for the two packets;
Schulzrinne, et al. Standards Track [Page 39]
[RFC 3550](https://www.rfc-editor.org/rfc/rfc3550) RTP July 2003
the relative transit time is the difference between a packet's RTP
timestamp and the receiver's clock at the time of arrival,
measured in the same units.
If Si is the RTP timestamp from packet i, and Ri is the time of
arrival in RTP timestamp units for packet i, then for two packets
i and j, D may be expressed as
D(i,j) = (Rj - Ri) - (Sj - Si) = (Rj - Sj) - (Ri - Si)
The interarrival jitter SHOULD be calculated continuously as each
data packet i is received from source SSRC_n, using this
difference D for that packet and the previous packet i-1 in order
of arrival (not necessarily in sequence), according to the formula
J(i) = J(i-1) + (|D(i-1,i)| - J(i-1))/16
Whenever a reception report is issued, the current value of J is
sampled.
The jitter calculation MUST conform to the formula specified here
in order to allow profile-independent monitors to make valid
interpretations of reports coming from different implementations.
This algorithm is the optimal first-order estimator and the gain
parameter 1/16 gives a good noise reduction ratio while
maintaining a reasonable rate of convergence [[22](https://www.rfc-editor.org/rfc/rfc3550#ref-22)]. A sample
implementation is shown in [Appendix A.8](https://www.rfc-editor.org/rfc/rfc3550#appendix-A.8). See [Section 6.4.4](https://www.rfc-editor.org/rfc/rfc3550#section-6.4.4) for a
discussion of the effects of varying packet duration and delay
before transmission.
Falon452
commented
11 months ago