/mcpTroubleshooting QoS Choppy Voice Issues Document ID: 20371 Contents Introduction Prerequisites Requirements Components Used Conventions Causes of Choppy Voice Bandwidth Requirement Voice Traffic Priority Serialization Delay VAD Typical Configuration Examples for QoS Jitter and Playout Mechanism Playout Mechanism Jitter Buffer Identify Delay and Jitter show call active voice show voice call <port−number> Configure Jitter Buffer on a Gateway Playout−delay Mode Related Information Introduction For Packet Voice to be a realistic replacement for standard public switched telephone network (PSTN) Telephony services, the received quality of Packet Voice must be comparable to that of basic telephone services. This means consistently high−quality voice transmissions. Like other real−time applications, Packet Voice has a wide bandwidth and is delay sensitive. For voice transmissions to be intelligible (not choppy) to the receiver, voice packets cannot be dropped, excessively delayed, or suffer varying delay (otherwise known as jitter). This document describes various Quality of Service (QoS) considerations that help troubleshoot choppy voice issues. The main reasons for choppy voice problems are lost and delayed voice packets. Prerequisites Requirements Readers of this document should be knowledgeable of these: Basic configuration of Packet Voice (VoIP, Voice over Frame Relay (VoFR) or Voice over ATM (VoATM) as per their requirement). • Basic understanding of voice prioritization, fragmentation, different codecs and their bandwidth requirements. • Components Used The information in this document applies to all Cisco voice gateways software and hardware versions.