Poll: Should PBXes fully support the G.729 vocoder? |
Definitely! |
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265 |
86.32% |
Maybe |
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23 |
7.49% |
What for? |
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19 |
6.19% |
Total: |
307 Votes |
100% |
Dia
Premium Account
Registration Date: 03.03.2006
Posts: 1443
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OK, let's run through this call scenario step by step. Please correct me if I am wrong, or if I omit a step.
An inbound call from the PSTN has arrived to your DID. The DID provider's SIP Proxy sends the call to the SIP URI voipswitchuser@PublicStaticIPofVoiPSwitch which in turn sends the call to a SIP UA which supports the G.729 vocoder. Apparently, this call scenario works as intended, with the G.729 vocoder being the common codec across all the call legs.
An inbound call from the PSTN has arrived to your DID. The DID provider's SIP Proxy sends the call to the SIP URI [email protected] which in turn sends the call to the SIP URI voipswitchuser@PublicStaticIPofVoiPSwitch that in turn sends the call to a SIP UA which supports the G.729 vocoder. Apparently this call scenario doesn't work as intended, since the G.729 vocoder is not the common codec across all the call legs. The call leg from PBXes to the VoiPSwitch is set to the GSM codec for some reason.
Here is the test call setup you should use to troubleshoot this: The DID provider's SIP Proxy sends the call to the SIP URI [email protected] which in turn sends the call to a PBXes extension that allows you to look at which vocoder has been chosen during the call. It is quite easy to see the vocoder on the Linksys SPAxxx and on the Snom phones, or you can setup a packet trace with any other SIP UA that doesn't indicate the vocoder during the call.
If after a few test calls, the vocoder happens to be the G.729 all the way through to the extension, then you will have verified the PBXes' G.729 Passthru feature works properly with this particular DID. Then set the Inbound Route to send the call through to an IVR before it sends it to the same extension. If the vocoder is GSM instead of G.729 then the IVR creates the transcoding issue.
Note: Snom phones are best for these kind of tests, since they support both the GSM as well as the G.729 vocoders, and their built-in SIP trace can be used as a reference.
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18.05.2010 22:34 |
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fra
Grünschnabel
Registration Date: 24.12.2006
Posts: 15
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18.06.2011 18:56 |
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