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New Member

Cisco IP Phone and codec type

Hi. Can you say, what codec type does IP Phone 7910 support and how can I restrict ip phone to use g711[a|u]-law or g729r8 in case of using ip phones with ip keyswitch feature. I didn't find link which exactly explains codec managment on ip phones.

Thanks.

3 REPLIES
Cisco Employee

Re: Cisco IP Phone and codec type

The 7910 ip phones support g.711[u|a]law and I believe they use g.729br8. G.729br8 works with g.729r8. What do you mean by restricting codec types on the ip phones? Can you explain more?

Thank you,

New Member

Re: Cisco IP Phone and codec type

In what cases does 7910 use g.711* or g.729* ?

By what is codec selection on ip phone defined when call is placed from ip phone and when call is placed to ip phone ? (Codec selection - what codec type must ip phone use)

Thanks.

New Member

Re: Cisco IP Phone and codec type

Have a look at device pools and regions this will explain something to as far as codecs go they are rated with a mos score g.711 around 4.1 and uses pulce code modulation and is 64kbps add the headers on a ethernet lan and you will see packet sizes of 214 bytes without the ethernet header 14bytes you get 50x200byte =10000(packets per second) x8 for bits =80kbps stream some one correct this if its wrong anyway you are enclined to use g.729 over wan links as it is less bandwith hungry though it requires alot more processing ACELP is the coding compression method used 3.7 is the mos score be aware that There are drawbacks to compressing voice. One of the main drawbacks is signal distortion due to multiple encodings (called tandem encodings). For example, when a G.729 voice signal is tandem encoded three times, the MOS score drops from 3.92 (very good) to 2.68 (unacceptable). Another drawback is codec-induced delay with low bit-rate codecs.

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