[Asterisk-Users] Zap Clocking - Frame Slips - tdm400p wcfxo zttest cpu spikes spandsp

[Rich Adamson]

> I've made some modifications to zttest in order to use
> it as a frame clock accuracy tester / slip detector.
> I'm not certain if that was it's original purpose, but it
> seems that a lot of folks try to use it that way.
> The result is something that I'm calling ztclock for now
> to help avoid confusion.
> <snip>
> Background:
> During routine codec/dimensioning testing, I observed a strange,
> recurring cpu spike occuring appoximately every 12 seconds on a
> completely idle system with only the zaptel drivers loaded. I used
> 'vmstat 1' to monitor this. I was using the wcfxo driver (wildcard
> fxo) as a timing source. 

So, chicken & egg: which comes first... the cpu spiking causing
missed data, or, missed data causing cpu spiking, or, none of the
above?

Compiled and ran on a cvs-head box with a TDM04b (4 fxo's) Rev H card,
fedora 3, 3ghz celery:

[root at phoenix zaptel]# ./ztclock
ztclock - clock source accuracy test (3 passes)
Flushing input buffer...
Flush Complete.
Test is approximately 3 minutes. Please wait...
483328 samples in 60.413670 sec. (483310 sample intervals) 99.996277%  
483328 samples in 60.413665 sec. (483310 sample intervals) 99.996277%  
483328 samples in 60.413670 sec. (483310 sample intervals) 99.996277%  
Estimate 8 frame slips every 26.851555 seconds.

I see the above appears to be slightly better then the numbers posted
in your example. Running spandsp fails on the above system with
nothing else running on this system (no calls, no nothing).

Can we draw any conclusions or limit assumptions given the output?

Rich