[asterisk-dev] Jitterbuffer and FAXes with E1

Steve Underwood steveu at coppice.org
Thu Jun 28 07:09:21 CDT 2007

Martin Vít wrote:
> Hello,
> I'm testing 1.4.5 (no modifications) with E1 card and i've found problem.
> I've this scenaro
> FAX -> SIP - ATA -> asterisk -> E1 port A --loopback--> E1 port B --> 
> iaxmodem.
> When jbenabled is off FAX is delivred OK. But when jbenable = on FAX are 
> failing in almost every line. I've compared WAV extracted from network 
> with WAV recorded (app monitor) before it gets to iaxmodem and there is 
> small differences. Network jitter is about 2ms (lab environment).
> Where could jitterbuffer modifies frames? I've tried to disable plc in 
> plc.c but without success. Any idea?
This is correct behaviour. Most VoIP kit has the ability to disable 
jitter buffering when a FAX is in progress.


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