[Asterisk-Users] Best CoDec for high network latency

[Guillermo Salas M]

Con fecha 28/1/2006, "Jean-Michel Hiver" <jhiver at ykoz.net> escribió:

>Guillermo Salas M a écrit :
>
>>Hi,
>>
>>I need to have some SIP extentions on remote places where the latency
>>from my asterisk box with public ip is 1~1.5 seconds.
>>
>>What codec will work fine on this sceneary? I'm planning to use iLBC, is
>>a good choice?
>>
>>
>There are basically three parameters I can think of when speaking of
>voice over ip quality:
>
>1 - Lag. In your case, a ping from your Asterisk box is 1 to 1.5 ms.
>Changing codecs is not going to help you here.
>

The lag if 1000 ~ 1500 ms


>2 - Jitter. In your case, if the ping does vary between 1 and 1.5,
>that's 500ms "ping jitter", which is high. You might want to have a
>large jitter buffer to compensate for it. But this increases lag even
>more...
>
>3 - Packet drop. iLBC is meant to cope "better" with packet drop than
>other codecs, although in my experience any codec with too much packet
>drop will sound dreadful.
>
>If you have the bandwith and no packet loss, I would recommend that you
>bump up the jitter and stick with ulaw. While there might be a lot of
>lag - "half duplex" kind of conversations... - the audio should remain
>clear.


I don't have packet loss, but my BW is limited.

>
>If you are having packet loss on top of this, you might want to try iLBC...
>
>At any rate, nothing is going to replace trying out some settings for
>yourself...
>
>BTW: How come the latency is so high? The worst I've seen so far was a
>link varying between 600 and 1200ms and the quality varied from "good
>enough" to "pretty horrible"...
>
>Cheers,
>Jean-Michel.
>
>--
>Jean-Michel Hiver - http://ykoz.net/
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