22 Jan
2007
22 Jan
'07
11:26 a.m.
Hi,
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...
regards,
Stefano
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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