Monitoring (Recording set to Always) - Low volume

torontob

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#1
Hi guys,

I have Recording set to Always and it all works fine and shows in Monitoring section. However, the outside party's sound is really low compared to internel extensions. I beleive both party's hear each other just well but it's the recording that has one side not recording very good. Is there any volume somewhere where I can boost the other party's volume a bit?

Thanks
 

dicko

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#2
torontob:

That would depend on the trunking you are using (you didn't say), my suspicion is that you are using zap trunks, because the nature of sip or iax2 trunks are intrinsically "normalized" as to sound level. If indeed they are Zap trunks, then I believe I can help you. If they are not then you will be left with the option of changing the V(x) and v(x) parameters used to call the underlying mixmonitor app. (unfortunately, you can't do that within FreePBX directly).

Dicko
 

agidi

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#3
Dear Dicko, im interested too in increasing the recordings volume on zap recordings, it is way too low, what did you have in mind?

thanks
 

dicko

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#4
There are two remedies, one longer than the other, so I don't confuse you, are the zap trunks TDM (T1's)(requires the long remedy) or just POTS (plain old telephone service)(a shorter solution)?
 

agidi

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#5
POTS :)

The TX RX gain levels, dont seem to work.

I'm all ears, or eyes in this case.
thanks
 

torontob

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#6
Dicko:

Yes, I am using Zap too and it's a Sangoma A400 infact with 20 channels. SIP are nomalized just like you said. So, I am interested in hearing what you have to say about Zap lines too.

Thanks
 

dicko

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#7
Briefly and in the absense of T/E1's

there is a tool
/sbin/ztmonitor

which is designed to tune your 2/4 wire hybrid. Which when called with:-

ztmonitor <chnum> -vv

will monitor in realtime the named channel.

Discover from your telco provider(usually little chance ther) or google a so called milliwatt test number. Call that number using the monitored channel and then iteratively adjust (as you alluded to) rxgain in /etc/asterisk/zapata.com, until the numbers on the right are around 13000 (in my experience).
there is a built in milliwatt application Milliwatt() in asterisk to check your txgain.

Changes to rxgain and txgain require an asterisk restart to take effect, zap reload is not enough.

In the absence of a milliwatt test-number then you can do "best effort" with a conversation and try and adjust to about 75%-80% modulation.

(once you have tuned your hybrid you will experience a significant reduction in echo also)
 

dicko

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#8
TDM circuits are a little different and here again PRI v. traditional T1's need separate handling.

There is usually a box that terminates the T1 circuit from the telco called by various names but often the CSU/DSU (Channel Service Unit/Data Service Unit). there are settings for both the ds1 side (network facing) and the dsx side (local switch facing) the attenuation of the ds1 side and the length of the dsx side also need properly tuning, sometimes by dip switches, sometimes by TTY (usually password protected by the telco) there are also parameters in /etc/zaptel.conf that can be tuned to match the build-out (in this case the two parameters are merged into one, as there is only one interface and it might point to the network or to another internal pbx. most manufacturers of hardware document these settings for you, I never used sangoma T's so I can't be authoritative here.
(Changing the zaptel.conf file requires further a zaptel/dahdi restart)

( A dsu is actually built into asterisk type TDM hardware but it is probably illegal to bypass the the telco hardware where you are, and possibly costly on your hardware so don't be tempted to take this shortcut)

These settings all have to be set to appropriate values before you go to the next step. Or unacceptable bit error rates, frame slips and so called BV (bipolar violations) will screw everything up. (A chain is a strong as it's weakest link)


The next step:-

The tuning procedure after setting up the external hardware is much the same but I have found that the right hand side parameters are, in this scenario, normally much lower than the POTS values for the milliwatt test, YMMV however.

The ultimate desire in this and my previous post are to realize a fully modulated, but unclipped audio signal in both directions on the 2-wire/4-wire hybrid.

I forgot to mention that ztmonitor's scale is log law not linear.

Just my 2cents worth,
It works for me.
 

torontob

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#9
Amazing! I listened to MCI milliwatt and I am surprised that my client didn't complain yet. If it wasn't for listening to their conversations (I am allowed to do that :)) then I wouldn't have noticed the problem. I hear them ask their clients to repeat over and over what they said and yet they didn't think of telling me of the problem. Anyhow, my rx = 13 and I my rx hovers around 1300 (I believe Dicko meant 1300 not 13000) and it sounds great.

For everyone else looking millwatt numbers in Canada try the following:

Provider Number
Bell XXX-958-2622 (Where XXX can be area code 416, 905, 519, etc...but your provider has to be Bell Canada)
MCI 1-800-444-4444 (Probably this is the best number to try as it seems to work with any provider)

By raising rx levels, I did notice some white noise at the beginning of the call which fades a bit as call continues. Since my Sangoma A400d has onboard Echo Cancel, I believe that is taken care of as the call continues, but again I could be wrong. I didn't test this with actual SIP phones on the premises but used two Zap lines to bridge calls and check the quality of recording.

-Bruce
 

dicko

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#10
torontob:

Indeed, I typo'd, mea culpa,
edit: - no in retrospect, I believe I will stand by my figure, the scale is logarithmic, I was speaking of analog trunks and that 13000 figure was specifically for agidi, who asked first, you have a T1, I said it would be significantly less for your deployment. (It's been a long time, and my memory fails me sometimes, further I haven't used an analog trunk since 1872 or thereabouts, so I can't verify, but the basic principal remains, full modulation with no clipping (subjective))

I'm glad you're learning to fish!, welcome to the anglers club. But I believe you might have an issue with Bell(or Rogers or whoever you use up there in the tundra) 13.0 db is a hellova lot, no wonder your hear noise!

Oh, and BTW, "You're welcome!". and I'm glad that, apparently, I didn't "waste my energy" this time.
 

torontob

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#11
Well, I put it down to 9 now and tested it with sending Milliwatt to voicemail and all seems fine.

AND, Thanks a lot for the ztmonitor trick Dicko!!!!!!!!!!!!!!!
 

agidi

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#12
a bit late, but I needed to thank you dicko!

that ztmonitor test is very interesting.

I had to put my rxgain to 17 to "fill" 85% of the audio level con a regular conversation.

thanks for the educating paragraph too.
much appreciated.
A.Gidi
:)
 

ramoncio

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#13
Very nice explanation indeed!
dicko, thanks for your invaluable help.
 

torontob

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#14
agidi: remember that if you ever get static on those lines due to rain or something then with value of 17 no one would understand each other. I found 9 to be suitable; I guess differnet providers require differnt gain levels.
 

agidi

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#15
Yes, it was too high. I had it good, on two of my test phones, but some people behind ATAs were complaining today. I lowered it a bit. I test and fine tune with use. Thanks for the advice.
 

Disaster

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#16
Hi Thank you for this useful information and it is what I need to solve my problem.

Now I have just started using Elastix and just installed Elastix 1.5.2-2.3 on Centos and the ztmonitor is not installed in the /sbin directory.

My question is how do install it has or has it been re named with Dahdi ?

Thanks
Eric
 

dicko

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#17
yes

dahdi_monitor
 

torontob

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#18
Now, I have added a Sangoma T1 card to the same system that has an A400D analogue Sangoma card. I hope that my rx of 9 won't do any damage to T1 settings since the rx settings in zapata.conf seem to be universal to both cards. Both cards are installed on the same system. Plan is to retire analogue one in about 1 month time once T1 PRI is fully tested to be working.

Any inputs?

P.S. Dick (guru!), is there anyway to display the ztmonitor or dahdi-monitor output onto a web GUI? maybe some php code? I want to show this in a nice bar like a sound bar and showing all channels that up and running. Hopefully this doesn't put a lot of strain on the system.

Thanks,
Bruce
 

dicko

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#19
I believe thatyou can put rxgain and txgain before each channel definition and it will be honored
 

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