Jitter

Jitter is the variance in the intervals when Interaction Media Server receives Real-time Transport Protocol (RTP) packets. For example, if Interaction Media Server constantly receives RTP packets every 20 milliseconds, there is no jitter. If the interval in the reception of RTP packets varies, such as 20 milliseconds, 45 milliseconds, 23 milliseconds, and 50 milliseconds, this variance is jitter. Many voice over IP (VoIP) solutions use a jitter buffer to collect multiple RTP packets within a time frame so that it can queue, reassemble, and retransmit the packets with a corrected, constant interval.

Interaction Media Server uses a jitter buffer for the following VoIP communications:

• VoIP calls that require transcoding from one codec to another.

• VoIP calls that contain call waiting tones.

• VoIP calls that contain intermittent tones that indicate that a call is recording.

• VoIP calls that contain digits from a dial pad interface in CIC client software.

• VoIP calls on CIC SIP lines with the Disable Media Server Passthru feature enabled.

For all other VoIP calls, Interaction Media Server does not use a jitter buffer and transmits the RTP packets as it receives them. For a CIC environment, this method of immediate transmission is known as a pass-through connection.

The jitter buffer for Interaction Media Server is dynamic. If Interaction Media Server detects variances in the receipt interval of RTP packets, it calculates an average receipt interval and then adjusts the jitter buffer to accumulate RTP packets within a time frame before retransmitting them. The maximum time frame for the jitter buffer in Interaction Media Server is 160 milliseconds, which equates to an average jitter of 53.3 milliseconds.

Significant variances in jitter can cause audio issues as the jitter buffer may not receive the expected number of RTP packets, which then causes Interaction Media Server to transmit silence where an RTP packet is missing. You can hear this silence as a brief break in an audio stream. Continual variances of this magnitude can produce ongoing breaks in the audio stream.

If you experience continuous breaks in audio streams, analyze each network node in the audio path and eliminate any bandwidth or processing limitations that cause jitter.