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Codecs with CMEs


I'm interconnecting two CME routers over a WAN. I have all of that working and can place calls between the two different extensions.

My questions relate to DSPs and codecs. I'm running G711 codecs to the handsets on both CMEs and G729a on the WAN VoIP peers.

I assume that when I dial between CMEs (an extesion 1xx dials a 2xx extension) I get 3 call legs:

Extension 1xx to CME 1 (G711)

CME 1 to CME 2 (G729a)

CME 2 to Extension 2xx (G711)

I assume that the transcoding between the different codecs on each call leg is handled automatically by the CMEs (i.e. I don't burn DSPs when I do this). Is this right?

Moving on, I have CUE attached to CME 2. When I call from a 1xx extension to a 2xx extension as soon as I get diverted to CUE, my call gets dropped. I have "allow-connections h323 to sip" configured. Reading a few articles, it suggests that I need transcoding available on the CME 2. I can't quite understand this as I'm transferring a call that was from CME 2 to 2xx handset (g711) to CME 2 to CUE (g711) - so why do I need transcoding? In any case, I've configured transcoding, and it still doesn't work. I've even tried changing the WAN codec to G711 and it still doesn't work :-(

Does anyone know of a design guide that covers interconnecting CMEs?

Thanks. Barry


Re: Codecs with CMEs


Re: Codecs with CMEs


Thanks for your response. Yup - have looked at this document (and a couple of others!). I've even managed to get transcoding configured and working (both CMEs are registered with my transoding sdsdfarm).

I guess my queries are more generic - what I'm after is a design guide that explain call legs / transcoding in more detail and how call legs / codecs relate to each other.

Thanks again. Barry

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