[Freeswitch-users] Sending t38 No-Signal packets while receiving a fax page with mod_spandsp

Steve Underwood coppice12 at gmail.com
Wed Nov 13 19:44:57 UTC 2019

On 11/13/19 6:03 PM, Daniel Greenwald wrote:
> Anyone know if freeswitch can be made to send periodic No-signal 
> packets while receiving a page data pump? Carrier's SBC is hitting an 
> RTP timer during long page transfers because freeswitch/spandsp is 
> completely silent while receiving a page. Other T38 switches I've 
> noticed will send a No-Signal packet every 300ms seconds as a 
> keep-alive. This can be seen in the top screenshot below. Lower one is 
> freeswitch receiving a page silently.

So, you've found yet another broken buggy system that doesn't follow 
standards. Surprise, surprise. If you find the person who made the 
system require no signal packets every 300ms can you find a 4x2 and wack 
them around the head with it for me, please?

There is an option in spandsp itself to make it regularly repeat the 
indicator signals, to tolerate this kind of broken behaviour. I'm not 
sure if the Freeswitch module exposes that capability.



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