Luki wrote:
However, when I execute
TxFax I see two g711 alaw packets going out for every one coming back, so my
outbound throughput is around 160kbps now. The second packet's payload
looks similar to the first, almost like a duplicate.
I'm no expert, but I think that's the redundancy intrinsic to T.38.
Steve Underwood had a page on T.38 but it's gone... Google's cache:
http://72.14.253.104/search?q=cache:6vjemQ-5rCsJ:www.soft-switch.org/t38/ch02.html
I am far from an expert myself, but from my understanding the fax
conversation starts out as standard RTP voice traffic (G711) and then
switches to T.38 when the receiving gateway (usually) detects a fax tone
- at least, this is the way the Cisco 5400's seem to operate. However,
my issue is that I am never actually switching over to T.38/UDPTL
transmission as the fax tone itself is not recognised and is coming
through as garbage to the other fax machine. I was wondering if it was
possibly related to the 2 x alaw packets being sent where I would
usually expect to see just 1? If there is some redundancy also built
into the initial RTP G711 conversation, I'm wondering if this can be
disabled somehow in the SpanDSP or OPBX code/config?
Cheers,
Ray
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