[Asterisk-Dev] is zttest actually working ?

[Andrew Kohlsmith]

On May 26, 2005 08:31 am, Rich Adamson wrote:
> Don't know about consensus, but would guess those that have looked
> at zaptel/zttest.c probably don't have sufficient zaptel background
> to form a strong opinion (including myself).

Agreed, but in general I have been agreeing with pretty much everything you've 
written to date on this.

a result < 100% indicates that you got the data EARLIER than the deadline, 
which is a *good* thing (to a point).  Since it just opens the zap pseudo 
channel your in blocking mode and you'll never get 8000 bytes even.  You'll 
get 8192 and you should get it in exactly 1.024s.  

> Personal opinion is that results from zttest code other then 100%
> is a problem, but the resolution within the code is insufficient to
> accuarately gauge the root cause for the variations. In other words,
> it seems that a variance somewhere between 99.97 to 99.99 is some
> sort of threshold, but there is insufficient output to even guess
> at what might be lurking to cause such a variance.

Well I see nothing wrong with coming in a few microseconds early, which is 
what the 99.9875-ish type results are all about.  You're absolutely right 
though; this is a pretty poor indicator of any serious issue.   Not having a 
whole lot to offer as an alternative though, I don't want to slam the 
authors.  :-)

> My focus in that effort was an attempt to discover why Steve
> Underwood's spandsp would not function correctly on a digium TDM
> analog fxo interface. I should probably note that spandsp has far
> more success on digium T1/E1 cards then it does on the TDM analog
> card, but the output from zttest on those two cards really don't
> point out why the differences. (Steve's past diagnostic efforts
> with several user attempts to run spandsp with the TDM card have
> consistently suggested the TDM card is missing chunks of data,
> but none of us know why. Since spandsp is attempting to function as
> an analog modem, any missing pcm data will obviously affect modem-type
> results even though the same missing data will not have that much
> of an impact on voice. I have personnally gone through every single
> suggestion including shared interrupts, pci latency settings, no
> other apps running on the system, changed kernels from v2.4 to
> v2.6, changed motherboards, swapping a TDM rev C card with a TDM
> rev H card (most current), changed IDE drives, etc, etc. I even
> dropped back to testing with a single digium x100p and got the same
> basic results.)

I don't recall if I've posted this nugget of information before, but I've 
heard that zaptel from 1.0.7 does *not* exhibit the "large CPU use every 5-6 
seconds" that HEAD does.  I haven't had much chance to really compare the two 
though.

-A.