[Freeswitch-users] DTMF

[Steven Schoch]

I had the opportunity to capture the data to/from the phone. I used this
packet capture command, on the FS host itself:

# /usr/sbin/tcpdump -p -s 0 -w jon.pcap -i eth1 host 192.168.4.235
10169 packets captured
10169 packets received by filter
0 packets dropped by kernel

The number dialed was 18002729872, the IRS EFTPS IVR.  The first voice
prompt is to enter the 9-digit taxpayer identification number.

In Wireshark, I can clearly see the numbers being entered, as RFC2833 RTP
DTMF events. One thing I notice is that I get several RTP packets for each
digit. (I assume that's normal, but I'm new at this.) For example, here is
one digit:

6507 87.427666 192.168.4.235 192.168.4.1 RTP EVENT 60 Payload type=RTP
Event, DTMF Two 2
6508 87.431287 192.168.4.1 192.168.4.235 RTP 214 PT=ITU-T G.711 PCMU,
SSRC=0x71C6FAAF, Seq=14414, Time=499365981
6509 87.447662 192.168.4.235 192.168.4.1 RTP EVENT 60 Payload type=RTP
Event, DTMF Two 2
6510 87.451285 192.168.4.1 192.168.4.235 RTP 214 PT=ITU-T G.711 PCMU,
SSRC=0x71C6FAAF, Seq=14415, Time=499366141
6511 87.467655 192.168.4.235 192.168.4.1 RTP EVENT 60 Payload type=RTP
Event, DTMF Two 2
6512 87.471284 192.168.4.1 192.168.4.235 RTP 214 PT=ITU-T G.711 PCMU,
SSRC=0x71C6FAAF, Seq=14416, Time=499366301
6513 87.487656 192.168.4.235 192.168.4.1 RTP EVENT 60 Payload type=RTP
Event, DTMF Two 2
6514 87.491286 192.168.4.1 192.168.4.235 RTP 214 PT=ITU-T G.711 PCMU,
SSRC=0x71C6FAAF, Seq=14417, Time=499366461
6515 87.507665 192.168.4.235 192.168.4.1 RTP EVENT 60 Payload type=RTP
Event, DTMF Two 2
6516 87.511285 192.168.4.1 192.168.4.235 RTP 214 PT=ITU-T G.711 PCMU,
SSRC=0x71C6FAAF, Seq=14418, Time=499366621
6517 87.527677 192.168.4.235 192.168.4.1 RTP EVENT 60 Payload type=RTP
Event, DTMF Two 2 (end)
6518 87.531284 192.168.4.1 192.168.4.235 RTP 214 PT=ITU-T G.711 PCMU,
SSRC=0x71C6FAAF, Seq=14419, Time=499366781
6519 87.547688 192.168.4.235 192.168.4.1 RTP EVENT 60 Payload type=RTP
Event, DTMF Two 2 (end)
6520 87.551336 192.168.4.1 192.168.4.235 RTP 214 PT=ITU-T G.711 PCMU,
SSRC=0x71C6FAAF, Seq=14420, Time=499366941
6521 87.567658 192.168.4.235 192.168.4.1 RTP EVENT 60 Payload type=RTP
Event, DTMF Two 2 (end)

This sequence happens 9 times with different numbers, as the 9-digit TIN is
entered. At 80.5 seconds (according to the Wireshark player), the called
party says: "The tax identification number must be nine digits. Please
re-enter." The last digit event was at timestamp 2495866430 (phone)
or 499404541 (FS). I don't know how to convert RTP timestamps to actual
time.

What's the next step to diagnosing the problem?

-- 
Steve


On Thu, May 9, 2013 at 1:14 PM, Michael Collins <msc at freeswitch.org> wrote:

> Are you sending in-band DTMFs or RFC2833? Or both? Get a pcap of the call,
> including the RTP, and analyze it in Wireshark. See what you are actually
> sending. That means looking at the flow (to see if you send RTPEVENTS, i.e.
> RFC2833 DTMFs) and also listening to the decoded audio with the player.
>
> -MC
>
>
> On Thu, May 9, 2013 at 12:59 PM, Steven Schoch <
> schoch+freeswitch.org at xwin32.com> wrote:
>
>> One of my users complains of many problems calling automated systems that
>> take DTMF input. In this case it was an IRS payment entry system that would
>> skip or duplicate button presses.
>>
>> Our setup is pretty generic:
>> Polycom SoundPoint IP 320 SIP -> dedicated LAN -> Freeswitch (on CentOS,
>> on XenServer) -> Comcast static IP -> Flowroute.com -> some IRS 800 number.
>>
>> Is this just the way it is, or is there something I can do to make it
>> work better?
>>
>> --
>> Steve
>>
>
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