a1200 with bad sound quality

When the scratchy occur, does the system lost interrupts? you can compile the zaptel with uncomment #define CONFIG_ZAPTEL_WATCHDOG in zconfig.h.

when interrupt lost occur, there will have log message in /var/log/messages.

another question, does the noisy call keep noisy until hangup? the noise occur from you pick to end?

i didnt find much about interrupts:
[code:1]cat /var/log/messages | grep interrupt
Jul 7 13:15:15 trixbox1 kernel: PCI: Firmware left 0000:01:08.0 e100 interrupts enabled, disabling
Jul 7 17:21:36 pbx kernel: PCI: Firmware left 0000:01:08.0 e100 interrupts enabled, disabling
[/code:1]

The scratchy noise will usually happen every few seconds through the whole call from beginning to end. I would rather try to solve this without recompiling.

Are there any buffer re-sync message in system log when noise occur?

So I migrated the system to a whole new platform using PBX in a Flash, everything is compiled from source:
* Asterisk Source Version  : 1.4.21.2
* Zaptel Source Version    : 1.4.12.1
* Libpri Source Version    : 1.4.9
* Addons Source Version    : 1.4.7
CentOS release 5.2 (Final) :32 Bit Kernel: 2.6.18-92.1.22.el5

I have made no modifications to zaptel other than what is instructed for the opvxa1200 module, it is running the standard MG2 echo canceler.

I ran zttest, after 100 passes it was still 99.96 at the worst, below is more:
--- Results after 1206 passes ---
Best: 100.000 -- Worst: 99.680 -- Average: 99.996785, Difference: 99.997571

What happens is the inside caller hears a scratching noise when he talks, the other person on the caller does not hear any problems, the call is perfectly clear for them. The noise is usually for the first 3-5 seconds of when the person talks, then it goes away.

messages log shows no lost interrupts. I have tested SIP trunks also and all SIP calls are fine, only calls through the fxo channels are scratchy.
these are the only sync messages, but there are calls every minute that get bad voice problems, maybe 300-400 calls per day.
$ cat /var/log/messages |grep buffer
Mar 3 04:46:19 pbx kernel: buffer sync misseed!
Mar 3 04:46:19 pbx kernel: buffer re-sync occur from -1 to 3
Mar 3 05:30:02 pbx kernel: buffer sync misseed!
Mar 3 05:30:02 pbx kernel: buffer re-sync occur from -1 to 3

i] Last edited by jahyde at 2009-3-4 08:22 [/i

"What happens is the inside caller hears a scratching noise when he talks, the other person on the caller does not hear any problems"

in this case , it should be other issue, not a h/w issue.

"$ cat /var/log/messages |grep buffer
Mar 3 04:46:19 pbx kernel: buffer sync misseed!
Mar 3 04:46:19 pbx kernel: buffer re-sync occur from -1 to 3
Mar 3 05:30:02 pbx kernel: buffer sync misseed!
Mar 3 05:30:02 pbx kernel: buffer re-sync occur from -1 to 3"

this means that the re-sync occured every 1 hour, it should not decrease the voice quality(supposing your system lost 1 irq in 1 hour)

still no idea with it, could you record the call and post here?