[Users] Support for T.38

Stefano Capitanio s.capitanio at caspur.it
Mon Jan 22 10:26:05 CET 2007


yes, there are a lot of problems using T.38 between two different UAs 
implementations (like your IP GW and your PSTN GW), but the SIP Proxy is 
not involved.
We have achieved better fax results using "pass-through" technique (with 
non-compressed codec G.711), but this is valid only if your IP network 
has a very low packet-loss rate...


Stephen Varga ha scritto:
> Max,
> OpenSER does not get involved with the media stream, it just handles 
> call setup and therefore does not generate FAX tones. It is up to the 
> UAs to negotiate CODEC used for the call. In the example you provided 
> of the call path, both the IP gateway and the PSTN gateway would have 
> to support the T.38 specification. If one side does not support T.38 
> they will most likely use a normal voice CODEC to handle the FAX tones 
> and FAX tones do not do well when compressed with voice CODECs.
> Steve
> Max Gregorian wrote:
>> Hi,
>> Does anyone know if OpenSER supports T.38 for Fax over IP?
>> Or has anyone managed to get it to work?
>> I did some quick tests and what I got was the destination Fax machine 
>> rang,
>> but the fax message did not arrive. I don't think the destination fax 
>> picked
>> up.
>> Setup was:
>> Fax (PC modem) -> IP Gateway -> OpenSER -> PSTN -> Fax machine
>> Is it possible the Fax tones are not being properly generated by 
>> OpenSER,
>> and so not being recognised by the Fax machine? (For reference, the 
>> Gateway
>> used is advertised as supporting T.38)
>> ------------------------------------------------------------------------
>> _______________________________________________
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>> Users at openser.org
>> http://openser.org/cgi-bin/mailman/listinfo/users
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