DAHDI sound breakup

Asterisk Asterisk Support
1

Hi,

I have the following problem at a client installation and he is very close to throwing the system out and going for another solution. For background, we are in South Africa (Gauteng Province)

  • All calls routing and connecting.
  • No hangups in calls
  • SIP connections are using codec G.711 (u and a law doing the same thing)
  • No audible echo
  • Silence suppression on FXS gateway off
  • Intermittently, certain calls from extensions (via SIP gateway) to PRI lines have sound breaking up. There are gaps in the sound, which is more noticeable on the SIP side.
  • However, SIP to SIP calls have very good quality
  • In the basic setup there is no NAT, all equipment connected to same switch (which has been replaced) in same room.
  • Call volume is about 350 calls per hour.

Setup
1 x HP ML110 G5 Server, Dual core pentium, 4 GB RAM, 250 GB HDD
1 x Digium TE121 with hardware echo cancellation connected to E1 line with PRI
1 x Grandstream GP2000 SIP phone
Multiple Octtel FXS gateways for extensions serving appr. 48 extensions
Elastix 1.5.2-2 with
Freepbx 2.6.0
Asterisk 1.4.24
DAHDI 2.2.0.2

DAHDI system.conf

# Span 1: WCT1/0 "Wildcard TE121 Card 0" (MASTER)
span=1,1,0,ccs,hdb3,crc4
# termtype: te
bchan=1-15,17-31
dchan=16
# echocanceller=oslec,1-15,17-31

# Global data
loadzone        = za
defaultzone     = za

chan_dahdi.conf

[code][trunkgroups]

[channels]
context=from-pstn
signalling=fxs_ks
rxwink=300 ; Atlas seems to use long (250ms) winks
usecallerid=yes
hidecallerid=no
callwaiting=yes
usecallingpres=yes
callwaitingcallerid=yes
threewaycalling=yes
transfer=yes
canpark=yes
cancallforward=yes
callreturn=yes
echocancel=yes
echocancelwhenbridged=no
faxdetect=no
; echotraining=800
; echotraining=no
echotraining=64
rxgain=0.0
txgain=0.0
callgroup=1
pickupgroup=1

priindication=outofband
inbanddisconnect=no

pridialplan=unknown
prilocaldialplan=national

;Uncomment these lines if you have problems with the disconection of your analog lines
;busydetect=yes
;busycount=3

immediate=no

#include dahdi-channels.conf
#include chan_dahdi_additional.conf[[/code]

dahdi-channels.conf

[code]; Autogenerated by /usr/sbin/dahdi_genconf on Thu Oct 22 10:25:03 2009 – do not hand edit
; Dahdi Channels Configurations (chan_dahdi.conf)
;
; This is not intended to be a complete chan_dahdi.conf. Rather, it is intended
; to be #include-d by /etc/chan_dahdi.conf that will include the global settings
;

; Span 1: WCT1/0 “Wildcard TE121 Card 0” (MASTER)
group=0,11

context=from-pstn

context=from-did-direct
switchtype = euroisdn
signalling = pri_cpe
channel => 1-15,17-31

[/code]

2

Followup:
Removed the hardware echo suppression module and the problem seems to gone.