VP-12, VP-12P IP phones. Operation manual
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Jitter Buffer
Jitter is a deviation of time periods dedicated to packet delivery. Packet delivery delay and jitter are measured
in milliseconds. Jitter value is higher for real time data transfers (e.g. voice or video data).
In RTP, also known as 'media stream protocol', there is a field for precision transmission time tag related to the
whole RTP stream. Receiving device uses these time tags to learn when to expect the packet and whether the
packet order has been observed. On the basis of this information, the receiving side will learn how to configure
its settings in order to evade potential network problems such as delays and jitter. If the expected time for
packet delivery from the source to the destination for the whole call period corresponds to the defined value,
e.g. 50ms, it is fair to say that there is no jitter in such a network. But packets are delayed in the network
frequently, and the delivery time period may fluctuate significantly (in the context of time-critical traffic). If the
audio or video recipient application will play packets in the order of their reception time, voice (or video) quality
will deteriorate significantly. For example, if the voice data is being transferred, there will be interruptions and
interference in the voice.
The device features the following jitter buffer settings:
•
Min Delay, ms
–
minimum expected IP package network propagation delay.
•
Max Delay, ms
–
maximum expected IP package network propagation delay.
•
Deletion Threshold (DT)
– maximum time for voice package removal from the buffer. The parameter
value should be greater or equal to maximum delay.
•
Jitter Factor
–
parameter used for jitter buffer size optimization. The recommended value is 0.
Input Gain Control
