Clarification Regarding the Jitter

Unanswered Question
Feb 13th, 2009

Hi ,

We are facing a sever sound disturbance in our IP phones . please find the MOS and Jitter values displayed in our ip phone .

Max Jitter as 53 , Avg as 5

and MOS value 2.5 .

Can anyone please clarify the below given questions .

1) what is the range of Jitter value in network , which will make ip phone to work without delay

2) Is it dependent of Codec .

3) What is the range of MOS can come in G 711 and G 729 codec

Regards ,

Sinjish.K

I have this problem too.
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Nicholas Matthews Fri, 02/13/2009 - 04:38

Hi Sinjish,

We start seeing problems when the jitter gets above 20 or 30ms.

You can check G.114 for details on just delay, but we find those values are a little liberal and voice quality starts to degrade slightly towards the ends of the G.114 values.

If you are getting voice quality problems due to jitter, if you press the '?' (or sometimes 'i') button on your 7960 twice quickly, you will get some stats during the call. If you have Rcvr Discarded packets, your jitter is causing voice quality problems.

Describes the problem in more detail:

http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a00800945df.shtml')">http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a00800945df.shtml

2) G729 is going to sound much worse than G711 if there is a dropped packet, due to the nature of the compression. G711 is more friendly to packet loss / jitter loss than G729.

3) Here are the MOS scores:

http://www.cisco.com/en/US/tech/tk1077/technologies_tech_note09186a00800b6710.shtml#mos

-nick

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