Spa2102 and Spa122 codec negotiation

[c.maggiolini]

Hi all,

we are facing a problem with codec negotiazion with SPA2102 and SPA122. The firmware version are the latest available for the two platform.
This is the scenario:
User A makes a phone calls via SPA2102 or SPA122 to User B on PSTN.
In the INVITE the SDP media description is RTP/AVP 18 8 0 101 and in the 200OK response from User B the m line is RTP/AVP 8 18 101.
The SPA2102 or SPA122 start sending RTP in G729 and the PSTN Gateway in RTP G711A.
The user on the PSTN doesn't hear the voice coming from SPA2102 or SPA122 because of the different codecs.

How can I force SPA2102 or SPA122 to switch to G711A when they receive 200OK response and RTP packets ?

Thanks
Carlo

[Dan Lukes]

The SPA2102 or SPA122 start sending RTP in G729 and the PSTN Gateway in RTP G711A

One codec in one direction and other in oposite is correct, althougth not common. It should work.

How can I force SPA2102 or SPA122 to switch to G711A when they receive 200OK response and RTP packets ?

Did you tried this ?

Administrator guide:

Use Remote Pref Codec

If set to yes, the phone communicates  using the remote phone's preferred codec. If set to no

...

[c.maggiolini]

Thanks for the suggestion. Tomorrow I'll give a try to see if it solves the issue for SPA122.

For the SPA2102 with firmware 5.2.13(004) it seems that that setting is not available in the menu. I'll give a read at the 2102 xml config schema to see if it's an "hidden" setting .
Regards
Carlo

[Dan Lukes]

By the way, if you are going to accept alaw offer from PBX, the you should consider it to set most preferred codec.

Using a-law on your side as most preffered codec will solve your problem as well. In advance, alaw have better quality, especially for FAX (or data) and in-band DTMF transmission.