[Asterisk-Users] Terrible crackling on analogue line and X100P card

[Damian Funnell]

Rich Adamson - would appreciate your advice as well, as your mail is the 
closest I have seen to a knowledgeable response so far in regards to 
this crackling issue.  I have a customer who has a very similar 
crackling problem and to date we have suspected it to be the ISDN BRI 
adapter and/or CAPI, as it affects calls in progress over the genuine 
TDM400P card (which has 4 FXS ports) and SIP simultaneously.

Although the nature of this problem seems to vary, the customer reports 
that the crackling usually starts when an external call is received at 
which time the crackling overwhelms all voice channels and everyone has 
to hang up and re-establish the calls (after which everything works fine 
again).

Could it be possible that a problem with the TDM400P could affect SIP 
calls on Asterisk as well?

I don't think I have an interrupt problem (see interrupt table pasted 
below) and the output of zttest appears to be ok (at least as good as 
99.96% accuracy), so we are stumped.  Linux, Asterisk and ISDN driver 
versions as follows.  Appreciate any help you can offer.

Cheers,
Damian.


1) Linux localhost.localdomain 2.4.21-4.ELsmp #1 SMP Fri Oct 3 17:52:56 
EDT 2003 i686 i686 i386 GNU/Linux

2) Asterisk 1.0.6 built by root at localhost.localdomain on a i686 running 
Linux

3) divas4linux_2_4_21_4_RHEL3_i686_SMP-104.345-1

***  zttest output  ***
--- Results after 43 passes ---
Best: 99.975586 -- Worst: 99.963379

***  End zttest output  ***

***  Interrupt Table  ***
[root at localhost root]# cat /proc/interrupts
           CPU0       CPU1
  0:   40674647          0    IO-APIC-edge  timer
  1:        969          0    IO-APIC-edge  keyboard
  2:          0          0          XT-PIC  cascade
  6:        282          0    IO-APIC-edge  floppy
  8:          1          0    IO-APIC-edge  rtc
 12:       7132          0    IO-APIC-edge  PS/2 Mouse
 14:       6650          1    IO-APIC-edge  ide0
 16:          0          0   IO-APIC-level  usb-uhci
 17:  406583244          0   IO-APIC-level  wctdm
 18:    5450488          0   IO-APIC-level  eth0
 19:          0          0   IO-APIC-level  usb-uhci
 21:   11834725          0   IO-APIC-level  DIVA 4BRI 15587
 23:          0          0   IO-APIC-level  ehci-hcd
 27:     339738          0   IO-APIC-level  a320raid
NMI:          0          0
LOC:   40673196   40672862
ERR:          0
MIS:          0

***  End interrupt table  ***

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Rich Adamson wrote:

>>I'm experiencing terrible trouble with crackling and noise on an
>>analogue line connected to an X100P (compatible) card. I've checked the
>>line with a normal analogue phone and it works fine, clear as a bell,
>>but any outgoing or incoming calls to Asterisk are almost completely
>>drowned out by loud crackling.
>>
>>I've attempted to adjust the RX and TX gains, but to no avail. There's
>>also an echo, but only one way. I'm assuming this is a separate issue so
>>I've not done much to investigate that, but I may be wrong so if it is
>>related does anyone have any suggestions?
>>
>>I never had this trouble with ISDN, but then I wouldn't would I? :)
>>
>>If anyone can wave a magic wand, or at the very least point me to a
>>website where I can get my own magic wand, please let me know.
>>    
>>
>
>What country are you in, and does the chipset on the compat card
>support the telco standards in your country?
>
>If the chipset doesn't match your telco standards, there is a high
>probability you won't get rid of the echo. If it does match, then try
> echotraining=800
> echocancel=yes
>
>Regarding the crackling noise, have you checked for shared
>interrupts (cat /proc/interrupts)?
>
>If you run "cat /proc/interrupts" every ten seconds, do you see
>calculated interrupt values of about 1,000?
>
>Go to /usr/src/zaptel directory and run
> ./zttest
>Do you get something close to 100% over some period of time?
>
>What version of asterisk are you running?
>
>
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