[Asterisk-Users] Audio problems on Zap & SIP, local network, not IRQ related?

[kjcsb]

I am trying to get to the bottom of audio clicks, pops, dropouts with my 
Asterisk server. These occur even when the system is under minimal load 
(e.g. 1 Zap device in a queue being played music on hold) and occurs with 
both Zap and Sip devices so isn't network related. The audio problems occur 
at the same time on all channels and seems to be when Asterisk "gets busy" 
and uses >50% CPU e.g. just after an announcement ("you are first in the 
queue"). However running ztspeed (which takes CPU usage to 100%) seems to 
have no impact on zttest numbers or the audio.

I have the following setup:
Fedora Core 4 2.6.16-1.2111 smp kernel
TDM400 with 2 FXO and 2 FXS modules
Various SIP devices
SCSI hard drives
2 x P3 processors 500 MHz
1GB RAM

Based on what I've read I would have thought that this setup could easily 
handle one call being played music on hold in a queue.

I have read 
http://www.asteriskguru.com/tutorials/pci_irq_apic_tdm_ticks_te410p_te405p_noise.html 
and various other postings to try and resolve this issue.

When I run zttest I get 99.987793% most of the time but occasionally it 
drops to 99.926758% which often corresponds with the audio degradation. I 
have, however, noticed audio degradation at 99.987793% and good audio at 
<99.87%.

I have followed the instructions on disabling the Linux frame buffer 
http://www.voip-info.org/wiki/index.php?page=Asterisk+disable+frame+buffer. 
(There was no graphic on boot and no vga entry in /boot/grub/menu.lst

I am not running X windows.

The processors are not hyperthreading.

I have disabled ACPI by adding acpi=off to /etc/grub.conf

cat /proc/interrupts indicates no shared IRQs
           CPU0       CPU1
  0:   21418593   21478150    IO-APIC-edge  timer
  1:        142         62    IO-APIC-edge  i8042
  8:          1          0    IO-APIC-edge  rtc
  9:          0          0   IO-APIC-level  acpi
 16:      60618      60379   IO-APIC-level  megaraid
 17:    4185189    4271566   IO-APIC-level  aic7xxx, aic7xxx
 18:    1589117         12   IO-APIC-level  eth0
 19:          0          0   IO-APIC-level  uhci_hcd:usb1
 20:   85250811   86274087   IO-APIC-level  wctdm
NMI:          0          0
LOC:   42898234   42898233
ERR:          0
MIS:          0

lspci -v
00:0a.0 Communication controller: Tiger Jet Network Inc. Tiger3XX Modem/ISDN 
interface
        Subsystem: Unknown device b100:0003
        Flags: bus master, medium devsel, latency 32, IRQ 20
        I/O ports at d800 [size=256]
        Memory at fe100000 (32-bit, non-prefetchable) [size=4K]
        Capabilities: [40] Power Management version 2

lspci -vb
00:0a.0 Communication controller: Tiger Jet Network Inc. Tiger3XX Modem/ISDN 
interface
        Subsystem: Unknown device b100:0003
        Flags: bus master, medium devsel, latency 32, IRQ 11
        I/O ports at d800
        Memory at fe100000 (32-bit, non-prefetchable)
        Capabilities: [40] Power Management version 2

No other device is using IRQ 20 (or 11)

Running zttool shows no alarms, IRQ misses on the TDM400P

cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 7
model name      : Pentium III (Katmai)
stepping        : 3
cpu MHz         : 498.847
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov 
pat pse36 mmx fxsr sse
bogomips        : 999.41

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 6
model           : 7
model name      : Pentium III (Katmai)
stepping        : 3
cpu MHz         : 498.847
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov 
pat pse36 mmx fxsr sse
bogomips        : 997.59

Does anyone have any further suggestions? I would really appreciate any 
other pointers.

Regards

Cameron