[cisco-voip] Jitter buffering on NEC phones

[Joseph Mays]

We have not chosen it, we're just not sure what parameter should be changed 
to change it from 80ms when we are using g711 codec and there is nothing in 
the config which specifically references g711.

----- Original Message ----- 
From: "Andreas Sikkema" <asikkema at unet.nl>
To: <cisco-voip at puck.nether.net>
Sent: Tuesday, February 21, 2012 8:22 AM
Subject: Re: [cisco-voip] Jitter buffering on NEC phones


>> phone.audio.rfc2833.dtmf.relay="0" phone.audio.onhook.dtmf.mode="1"
>> phone.audio.pcmu.pref="4" phone.audio.pcma.pref="5"
>> phone.audio.g722.pref="3" phone.audio.g729.pref="6"
>> phone.audio.g7221.24kbps.pref="1" phone.audio.g7221.32kbps.pref="2"
>> phone.audio.g729.vad="1" phone.audio.pcmu.ptime="80"
>> phone.audio.pcma.ptime="80" phone.audio.g722.ptime="80"
>> phone.audio.g729.ptime="80" phone.audio.g7221.24kbps.ptime="80"
>> phone.audio.g7221.32kbps.ptime="80"
>>
>> The codec we are using is G711, so it's probably among the default 
>> values,
>> rather than the values aimed specifically at g722 or others.
>
> And
>
>> Almost all of the issues identified by wireshark at 50ms jitterbuffer are
>> packets dropped for exceeding the jitter buffer.
>
> That's because you have the packetization time set to 80ms, even for
> G.711 (pcma or pcmu depending on which G.711 you're using). Those
> values are not settings I see very often, so it's probably no wonder
> that endusers are complaining. Since 80 msec between each packet is
> larger than the wireshark jitterbuffer so every other packet is being
> dropped especially since the wireshark jitterbuffer is not adaptive as
> far as I'm aware.
>
> Is 80ms a value you've chosen yourself? Usually these are 20 or 30ms...
>
> -- 
> Andreas Sikkema
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