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

[Rich Adamson]

> 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).

So far, the three people that have complained about crackling noise are
all running the Stable version of asterisk. I have only used cvs-head,
and I'd be real curious if there isn't something wrong with Stable.
 
> Could it be possible that a problem with the TDM400P could affect SIP 
> calls on Asterisk as well?

I would doubt that simply because there are a lot of TDM cards in use
and only a small number that are complaining about the crackling noise.
I've not had that problem with either the original TDM or with the
most current TDM version.
 
> 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.

My best guess (in order of what I'm guessing the problem to be):
 - Stable version might have a problem
 - Interrupts (eg, disk activity impacting TDM interrupts)
 - half vs full duplex ethernet connection (look at output from "dmesg")
 - old TDM card version (ver E/F, look at output from "dmesg")

FWIW, the digium TDM card has a two year warrantee and it was first
released about a year ago. Therefore every TDM card is still under
warrantee. If you have a ver E/F card, I'd strongly suggest calling
digium support to have it replaced, regardless of where you are
located.

Our old TDM rev E/F would completely fail about every week or two, and
the only way to restore operation is to stop asterisk, stop the drivers,
and restart both. On _some_ occations, the card would fail in such a
way as to create nothing but noise, but that was not very often for 
our system.