VM Beep . . . What the Beep!

Discussion in '3CX Phone System - General' started by GManNAtl, Feb 14, 2013.

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  1. GManNAtl

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    OK, I have been in telecom for a while and have never seen anything like this.

    We had an outside company that we deal with quite frequently. Every time they left a voicemail, the beginning 8 seconds were silence. After getting some captures I had determined is was not an issue with RTP. Packets were being received fine so it was simply silence from the remote end. After some head scratching I thought that maybe the default "beeptone.wav" that is used to signal the start of recording was somehow being interpreted as DTMF by the remote PBX. So, off to the net for a new tone I could swap it out with and wallah everything worked fine! The VM's from this company are now fixed and no longer cuttoff.

    The bad news is the problem seems to be affecting other company's systems now. I have two users that are now reporting this quite regularly. The new tone we selected is more of a chime sound, so I don't understand why this is happening. It is certainly not being confused with DTMF at this point.

    Could it truly be the remote end, or could 3CX actually be getting confused by it's own tone?
     
  2. leejor

    leejor Well-Known Member

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    DTMF is comprised of two specific tones for each digit. Most "notification" tones only consist of a single frequency. I suspect that there is something else involved here.

    Do you have any idea of what type of PBX or equipment is being used there? I'm wondering why a DTMF tone would cut off the call to begin with.

    I know that gateways and ATA's, at times, will misinterpret speech as DTMF, , and then re-generate the tone. You might try using a single 1000hz tone, and see how that goes. You should be pretty safe with that.
     
  3. GManNAtl

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    I went online and found a 1000 hz tone. Converted it to the proper format, copied it to the server and no joy. The problem is consistent with the caller and if I swap these files back and forth either caller will exhibit the same behavior. With the original tone in place it only seems to affect some government offices that call us. When I have changed it to pretty much any other tone it affects a number of callers in the same way. I have three different providers for our service and it doesn't seem to matter which provider or gateway the call comes in on.
     
  4. leejor

    leejor Well-Known Member

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    That sort of indicates that if you do some digging, you are going to come up with a common denominator somewhere, caller, provider, type of gateway, etc. If it were a 3CX issue, then i can't believe that will all of the installations out there, that someone else hasn't had the same problem. There have been a few other posts recently with "missing" voicemail audio problems.

    You said that it seemed to be only one group of callers (one originating PBX?) having problems, is that still the case?
     
  5. GManNAtl

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    As it turns out, it does seem there are quite a few others that have had this exact same issue going back to v9. Initially, I had a Sangoma Gateway and I felt it had something to do with the gateway. I kept telling this one user that when we moved to SIP Trunking it would likely go away. When it didn't I looked at everything. When getting a wireshark trace everything looks perfect, and I do in fact receive a constant stream of RTP packets from the remote end. They are simply silence. So, you think aha it's the remote end. However, by just changing the tone the problem completely stopped for this caller (Government Social Security Office's).

    As stated above though, after doing this it works perfectly for these offices and now is affecting other callers. The problem is actually more widespread now and I can't nail it down to any one caller.

    I fear this is one of those problems that may never get resolved. I have an open ticket with 3CX now and will be getting some pcap's back to them. The problem is that from our/3CX's perspective the remote system is somehow "muting" the call and are not sending audio. However, I KNOW this is not the case. I can change the tone in the 3CX and completely change the behavior. It is 100% consistent with these offices which is . . . Default beep.wav = Miss 8 seconds of audio - New beep.wav = Works perfect. The SSA offices are not changing anything on their end to make it behave differently. I am unsure of what PBX they use, but I would suspect it is Cisco, and it occurs from EVERY SSA office we work with. The problem is compounded by the fact that I can't just keep bothering them to leave messages for us to test. They are pretty bothered by it already and I can't expect them to just keep calling in for us.
     
  6. tsteffens

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    Have you gotten 100% resolution to this? I have just run into this when I installed a 3cx system for a client and they started calling us to our 3cx nfr and I was missing 7-10 seconds of the voicemail. Digging into with 3cx support they determined that in the first 10 seconds or so the patton on the remote end(my clients) was trying to use Payload type: DynamicRTP-Type-127 (127) and then after 10 seconds it reconnects and uses 711ulaw.

    I have kind of suspected now that it has to do with the beep.wav file that plays. I cannot figure out how to change it and have tried to change it in the prompt sets and restarted the services but it doesnt seem to stop it from playing.

    Can you provide the beep.wav file you used and how you changed it?
     
  7. tsteffens

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    I found a solution to this. This had to do with a patton 4970 we were using at a clients site. When the voicemail on our end would beep it would change the codec of the call signalling something with the beep was being interpreted. Worked with Patton support and they had me disable modem on the device because the unit was switching to a modem mode when the beep would play. I hope this helps someone else in the future!
     
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