What is Jitter?
Jitter is variation in the arrival time of voice packets. It is the most common cause of choppy or robotic VoIP audio, and it is a separate problem from insufficient bandwidth.
Voice is sent as a steady stream of small packets, typically one every 20 milliseconds. If they arrive at uneven intervals, the receiving device has to decide whether to wait for a late packet or play what it has. Either choice degrades the audio.
A jitter buffer absorbs small variations by holding packets briefly before playback, at the cost of added latency. Buffers handle normal network variation; they cannot rescue a connection where variation is large or bursty.
This is why upgrading internet speed often fails to fix bad call quality. A connection with ample bandwidth can still deliver packets unevenly if voice traffic is competing with downloads. Prioritising voice with QoS on the router addresses the cause; a faster line usually does not.
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