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

Sun Mar 3 18:56:09 UTC 2013

If you have a system where you drive the modulator directly and use

txprelim=yes

-          then you already have limiting

If not, and you are using "microphone audio" then you should un-comment

txlimonly=yes

it is quite possible to overdrive the URI and it sounds nasty when it
happens.

(You should check that the values for txtone and txvoice that you used in
your audio calibration add up to a number less than 1000).

GL

Ken

From: app_rpt-users-bounces at ohnosec.org
[mailto:app_rpt-users-bounces at ohnosec.org] On Behalf Of Keith Goobie
Sent: Sunday, March 03, 2013 12:19 PM
To: REDBUTTON_CTRL
Cc: APP RPT
Subject: Re: [App_rpt-users] Audio Clipping with IAXRPT / Web Transceiver
Client

Hi Jon

Just checked the configs - 

All three appearances (we control three URI fobs) of txlinonly are commented
out, do you know what the default is.

Incoming audio from iaxrpt users seems OK, with no issues.

Keith

On 3/3/13 11:41 AM, "REDBUTTON_CTRL" <jrorke at cogeco.ca> wrote:

  Hi Kieth, In the usbradio.conf  have you got the "txlinonly = yes'? 

 This should limit TX audio coming from the URI.

 txlimonly=yes        ; Audio limiting with no pre-emphasis on output
channel: no,yes
             ; no - Audio is not limited. 
             ; yes - Audio is  limited.
             ; Suitable for transmitters with no limiting but with
pre-emphasis.

 You can also tell the IAX users to cut back their mic gains. I would start
here first. Like a lot of people on Echolink they dont have the computer set
up properly. I find that head sets sound the best rather than using the
internal mics on lapatops.

 I would leave the codec as Ulaw. dont bother with GSM, has crappy watery
audio.

 Jon VA3RQ

 On 3/3/2013 11:31 AM, Keith Goobie wrote: 

Audio Clipping with IAXRPT / Web Transceiver Client 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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-- 
keith at goobie.org
Keith Goobie
Richmond Hill, ON, CANADA

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