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IP Telephony: Packet-based Multimedia Communications Systems by Jean-Pierre Petit, David Gurle, Olivier Hersent

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Chapter 4. Voice quality

Introduction

A common joke among IP telephony engineers is to say that if they had proposed to carry voice over IP a couple of years ago, they would have been fired. This remains a private joke until you make your first IP phone call to someone who does not own a headset, and find out that the only person you hear is yourself.

Another way to find out why there really is a problem with IP telephony is to try a simple game: ‘collaborative counting’. Collaborative counting has a simple rule: if you hear the person you talk to say ‘n’, you immediately say ‘n+1’. In order to compare classic telephony with IP telephony, you first make a regular phone call to someone you know and say ‘1’, he goes ‘2’, etc. Keep an eye on your watch ...

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