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DTMF In vs. Out


andrewgroup
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2.1.5 and 2.1.6 fails DTMF detection calling from Cell Phones with Inband DTMF set to ON or OFF. Land line callers appear to work O.K. with on settings

 

2.0.3.1715 (Win32) with set to on works fine with our ITSP, OFF fails as above.

 

2.1.5 with an Epygi PRI E1 gateway is working fine with this set to OFF

 

How might we isolate or improve on this detection?

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On log level 9 (media) there is a way to see what the inband DTMF detector is doing. You can use this to see if there s a problem with the power levels for DTMF.

 

You should see something like "DTMF: Power: 122 34 322 343 535 345".

 

Our ISP has provided the following commentary.

We have it set up for auto negotiate for inband / outband but we find that other voip networks do not understand "auto" in the dtmf world. Wireless is a big issue since most carriers have moved to using voip for nearly 100% of their backhaul. we error toward inband; but we can tell you that you might still have an issue on 1 out of 100 calls requiring dtmf - we find this to be the case with large queue systems like an fed ex / ups. Their older systems do not handle the inband very well.

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I recently had a disussion with a very large carrier and a guy that really understands SIP and the whole VoIP story. DTMF is one of their biggest problems, and the only common denominator is inband. "Transcoding" DTMF is very very difficult, if not impossible. That is the sad truth and we should not hit too hard on the service providers, they really have a difficult position.

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With 2.0.3.1715 (Win32) and log level 9 Media we see

 

8] 2008/02/07 12:49:15: Play recordings/att6.wav space20

[6] 2008/02/07 12:49:19: Received DTMF 2

[6] 2008/02/07 12:49:20: Received DTMF 0

[6] 2008/02/07 12:49:20: Received DTMF 1

 

 

Switching DTMF inband off we see no logging events?

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We have inband DTMF issues as well. We cant get DTMF from CDMA cell phones. Our carrier is implementing RFC2833 so we are relieved (as a VAR). we will start selling ITSP pbxnsip again soon! :)

 

Funny thing I was in vegas this week and called a customer who has DTMF issues and it worked! Sprint CDMA went back to Utah, now it doesnt work! what crap i say!

 

Asterisk works just fine. pffft Good thing we use Exchange2007! take that DTMF.

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We have inband DTMF issues as well. We cant get DTMF from CDMA cell phones.

 

More details

From Sprint Cell Phone. It's acting as if isn't even seeing the touch tones. Revert back to 2.0.3.1715 (Win32) and all is OK....

 

[9] 2008/02/09 16:24:33: DTMF: Power: 0 0 0 0 0 0 1 0 0

[9] 2008/02/09 16:24:33: DTMF: Power: 0 2 0 0 0 2 0 0 0

[9] 2008/02/09 16:24:33: DTMF: Power: 0 0 0 0 0 0 0 0 0

[9] 2008/02/09 16:24:33: Last message repeated 5 times

[9] 2008/02/09 16:24:33: DTMF: Power: 2 0 0 0 0 0 1 0 0

[9] 2008/02/09 16:24:33: DTMF: Power: 0 0 0 0 0 0 0 0 0

[9] 2008/02/09 16:24:33: DTMF: Power: 0 0 0 0 0 0 0 1 1

[9] 2008/02/09 16:24:33: DTMF: Power: 0 0 2 0 0 0 0 0 1

 

 

From Land Lines V2.1.6 beta worked Fine. Here are the level 9 Media logs at or near when I entered the final extension digit and account greeting was played.

 

[9] 2008/02/09 16:28:20: DTMF: Power: 0 0 0 2 0 0 0 0 0

[9] 2008/02/09 16:28:20: Last message repeated 2 times

[9] 2008/02/09 16:28:20: DTMF: Power: 0 0 0 0 0 0 1 0 0

[9] 2008/02/09 16:28:20: DTMF: Power: 53 2 2 2 2 71 1 1 0

[9] 2008/02/09 16:28:20: DTMF: Power: 60 4 0 0 0 80 1 0 0

[6] 2008/02/09 16:28:20: Received DTMF 1

[8] 2008/02/09 16:28:20: Play audio_en/aa_say_extension.wav recordings/name1.wav

 

NexSIP posts similar troubles as Sprint is CDMA I think, but if the Sprint is working with V 2.0.3.1715 how would that be affecting V 2.1.6 10 seconds later after swapping pbxctrl?

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[9] 2008/02/09 16:24:33: DTMF: Power: 0 0 0 0 0 0 1 0 0

[9] 2008/02/09 16:24:33: DTMF: Power: 0 2 0 0 0 2 0 0 0

[9] 2008/02/09 16:24:33: DTMF: Power: 0 0 0 0 0 0 0 0 0

 

Whow that is really very silent. The threshold is 50, and those values are far away from that.

 

The problem is probably that we do the algorithm in fixed point, 32 bits. That is a must in the embedded world, on the PC we could use floating point. Maybe we can solve the problem by having a DTMF gain (at least available as static setting), I have prepared a build at http://www.pbxnsip.com/protect/pbxctrl-2.1.6.2442.exe that contains a global setting with the name dtmf_gain. The default is 256, which means factor 1. 512 would be factor 2 and so on. Maybe you can try this version and see how far we have to amplify in order to get the cell phone DTMF working... and of course it would be interesting if landline still works!

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global setting with the name dtmf_gain. The default is 256, which means factor 1. 512 would be factor 2 and so on.

 

I searched the entire interface looking for this setting, did I miss it somewhere?

 

Status does shows the new beta version.

 

I see no new setting on the admin settings screen and or it's 12:00 midnight, and I can't see it.

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It is in the Global Configuration File, http://wiki.pbxnsip.com/index.php/Global_Configuration_File. Yes, it is invisible - in this case for a good reason!

 

Then the following should create the necessary entry?

 

http://localhost/reg_status.htm?save=save&dtmf_gain=512

 

execute this command after logging into the web interface? if so, it did not create an entry for the dtmf_gain setting...

 

What common editor would you recommend not to clobber the utf format settings?

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Yes, that link should do the trick. You can use for example notepad to edit the file. First check if the file now contains the setting, then if that is the case you don't have to edit it.

 

I logged onto the box with admin, I executed the link, the entry is not in the file as far as I can tell. Open the file with IE and search fot dtmf or gain on the page and no results except for a show gain setting. Using notepad doesn't give me the confidence that I'd do the manual edit correctly as it displays on a very compressed format. Any recommended small footprint tools to edit this file would be recommended.

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I've found a nice easy to use XML editor at http://pollo.sourceforge.net/ requires only the addition of java to a windows machine. With it I've added the following entry for the PBX. I placed it as the very first item. Now knowing that hidden files exists, how many more exist?

<pbx-config>

<dtmf_gain>512</dtmf_gain>

<log_level>9</log_level>

 

now with 2.1.6.2442 (Win32) running the results are;

 

dialing from a POTS land line the log entries are

[9] 2008/02/10 15:02:20: DTMF: Power: 65 4 1 2 1 91 5 1 0

[9] 2008/02/10 15:02:20: DTMF: Power: 227 14 0 2 2 307 5 1 1

[6] 2008/02/10 15:02:20: Received DTMF 1

[8] 2008/02/10 15:02:20: Play audio_en/aa_say_extension.wav recordings/name1.wav

 

the DTMF 1 is the last of a three digit extension and it worked fine

 

now for the Sprint Cell Phone test.....and the results are......Voila' DTMF detection worked and the logs are

[9] 2008/02/10 15:05:36: DTMF: Power: 0 0 2 0 2 2 0 0 0

[9] 2008/02/10 15:05:37: DTMF: Power: 37 1 0 2 2 38 2 0 0

[9] 2008/02/10 15:05:37: DTMF: Power: 93 6 0 1 0 91 2 1 1

[9] 2008/02/10 15:05:37: DTMF: Power: 95 5 0 0 2 93 2 0 0

[6] 2008/02/10 15:05:37: Received DTMF 1

[8] 2008/02/10 15:05:37: Play audio_en/aa_say_extension.wav recordings/name1.wav

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Well the PBX runs the Goertzel algorithm (see http://en.wikipedia.org/wiki/Goertzel_algorithm), as most other applications that look at only a few lines in the spectrum. By default, the algorithm is in floating point. Then the threshold is easy to dertmine. Obviously we are fighting problems with fixed point arithmetic, and in order to solve this we just "amplify" the signal by the value dtmf_gain / 256. If you have really loud signals, there will be distortion - but it seems that DTMF is always relatively silent so that danger is not too high.

 

BTW we are also looking at the FAX CNG tone (that is the tone in the middle of the 9 values), that should make it possible to detect FAX in the auto attendant.

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If you have a FAX, check out the latest image http://www.pbxnsip.com/protect/pbxctrl-2.1.6.2443.exe. Set a direct destination of "F" to your FAX extension in the auto attendant and see if the PBX redirects the call to the FAX device.

 

I don't have a FAX here... Obviously I was able to survive without it!

 

We'll use both a Linksys supura ATA and a Patton ATA for testing. We'll get this tested Monday or Tuesday

 

How about a screen capture of what that Direct destination "F" is to look like...?

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NexSIP posts similar troubles as Sprint is CDMA I think, but if the Sprint is working with V 2.0.3.1715 how would that be affecting V 2.1.6 10 seconds later after swapping pbxctrl?

 

Its Verizon CDMA as well... thing i dont understand is why my Sprint CDMA actually worked in Las Vegas (unless maybe the long haul carrier converted the DTMF)

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