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fishtech

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Hi,

The Operator online help states that "For transmission, codecs will be used by priority (order) set in Selected codecs."

My phone handsets (Snom) also have a priority order which is set using the web interface of the phone.

Please advise which order takes priority. Also, is there a way to show which codec was used during a call? (I looked in Operator's SIP and Asterisk logs, and also the handset's SIP Trace already).

Thanks,

ft.

[Updated on: Thu, 06 September 2012 16:21]

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Vladimir Toncar (Kerio)

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Hi,

Both lists of codecs are taken into consideration. If party A sends a list of codecs [G711-ALaw, G711-uLaw, GSM], it means that its most preferred codec for receiving audio is G.711-ALaw, and that it can send audio in any of the three codecs.

Suppose the party B advertises its codecs as [G.711-uLaw, G.711-ALaw, GSM].

So during the call between A and B, the codecs will be used as follows:

A -> G.711-uLaw -> B
A <- G.711-ALaw <- B

The recommendation is to set the codecs so that you minimize transcoding from codec to codec (i.e. have the same priorities on both sides).

It's not yet possible to display the codecs used during the call in the Administration GUI but we will consider this for a future release.

Vladimir
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fishtech

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Thanks for the info.

For an out going call, does the Operator codec-order setting for the extension take precedence over the code-order setting on the handset?

Thanks,

ft.
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Vladimir Toncar (Kerio)

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Technically, these are two calls (or "call legs") connected in the middle by Operator, and each of them negotiates its own codecs. If the two call legs use different codecs, Operator needs to transcode from one codec to another.

Vladimir
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fishtech

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Thanks.

If an outgoing call is made via PRI, does the leg from handset to Operator default to g711, even if the handset is set to prefer g722?

Thanks,

ft.
  •  
Vladimir Toncar (Kerio)

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If the handset prefers G.722, Operator will trans-code from G.711 (used by the PRI) to G.722.
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fishtech

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OK, thanks for the info.

We like the quality of g722 locally (all our handsets support g722) but want to avoid transcoding on outside calls.

Is there any way to set g722 codec for internal handset-to-handset calls, but have Operator force g711 for outgoing calls router via the the PRI trunk ?

Thanks,

ft.
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Vladimir Toncar (Kerio)

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Hi,

It's not possible to switch codec priorities in the way you describe. Unless you have plenty of concurrent calls, transcoding should not be an issue. Also, translating from G.722 (an "HD" codec) to G.711 should not bring noticeable degradation in sound quality.

Vladimir
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