[App_rpt-users] Audio Clipping with IAXRPT / Web Transceiver Client

[Keith Goobie]

Good day All.

We have had our node up at VE3LSR / VE3UOR for a few months and we all have
learned a lot about configuration and operation.  It is ACID install and
version id is 300.3.

On our asterisk system, we support three nodes:

27211 ­ VE3UOR UHF repeater
29133 ­ VE3LSR coupled through a RLC-DSP404 controller (often connected to
VE3UPS and VE3UHN), and
29154 ­ VA3LSR remote link for VE3LSR into VE3MUS ­ not too active ­ ad-hoc
RF link.

I have also been testing out iaxrpt and the WebTransceiver clients.

I am on these systems and the results have been promising.  I do notice some
clipping on the audio on some stations.  Initially I thought it was
amplitude related ­ over-driving the URI-FOB, but I am now beginning to
suspect that it may be network related and in my research I hear the term
jitter being used ­ which if activated, adjust operation on the receiving
end only.

It may be that the system is not powered enough to drive the three uri-fobs.
CPU show about 25% busy.
[root at VE3LSR etc]# cat /proc/cpuinfo
processor    : 0
vendor_id    : GenuineIntel
cpu family    : 15
model        : 4
model name    : Intel(R) Pentium(R) 4 CPU 3.00GHz
stepping    : 3
cpu MHz        : 2992.898
cache size    : 2048 KB
physical id    : 0
siblings    : 2
core id        : 0
cpu cores    : 1
apicid        : 0
fdiv_bug    : no
hlt_bug        : no
f00f_bug    : no
coma_bug    : no
fpu        : yes
fpu_exception    : yes
cpuid level    : 5
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat
pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe lm constant_tsc pni
monitor ds_cpl est cid cx16 xtpr
bogomips    : 5985.79

We do think that the system is sufficiently powered.

We are looking for comments & guidance.  Are we expecting too much from the
system having three fobs connected?  We do have good bandwidth into and out
of the site.  

I am listening to other systems ­ most not to busy, so I am not yet able to
get a good reference point.

I have not dabbled with the codecs much, but have been focused on using
ulaw.  I am also testing with GSM ­ lower bandwidth.

So as I said before, thoughts or suggestions are welcome.

Keith / VA3YC
-- 
keith at goobie.org
Keith Goobie
Richmond Hill, ON, CANADA

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