[Freeswitch-users] DTMF bleed through in conference

[David Bolen]

Kristian Kielhofner <kris at kriskinc.com> writes:

> Agreed.  Sounds like an analog device not clamping inband DTMF -> RFC
> 2833 events properly (or quickly enough).
>
> Grab a pcap and look at the audio.  See if you can see DTMF in the
> audio stream itself.

Thanks.  I do believe the problem is while tones are using RFC2833.  I
did some separate in-band testing (manually configuring the PAP2T for
in-band and using start_dtmf on the switch) and in that case full
tones go through to the conference while also being recognized (though
in that case by switch_ivr_async, not switch_rcp).  What I hear in the
2833 case is a more truncated/clipped "blip" of sound.

I just ran a specific test with two conference participants - blink on
a Mac (software sipphone), and an analog phone through a PAP2T.  Both
connections direct to the FreeSWITCH server, no PSTN gateway involved.
I used blink as the DTMF generator.

I pressed "4" 4 times in blink, 3 of which (cases 1,2 and 4) were
audible blips to the other phone.  A summary of the blink outbound rtp
is at the bottom.  It seems to have the c101 types properly for the
presses.  Not sure if the occasional repeated sequence number is an
issue.  The pcap for the outbound leg is entirely c0 rtp types.

I used wireshark to generate audio files from the inbound blink leg
and the outbound PAP2T leg of the call and verified that the inbound
leg from blink to FreeSwitch was silent, while you can clearly hear
the brief blips of tones on the outbound leg.  So whatever is
happening (even if not FreeSWITCH but networking or some other host
issue) doesn't appear to be the end device(s).

-- David

Inbound packets (sipphone -> FreeSWITCH):
  17:23:24.954474 udp/rtp 160 c0  6611 197118243 1533652571
  17:23:24.973732 udp/rtp 160 c0  6612 197118403 1533652571
  17:23:25.053559 udp/rtp 4 c101 * 6613 197118723 1533652571
  17:23:25.053588 udp/rtp 4 c101 * 6613 197118723 1533652571
  17:23:25.053594 udp/rtp 4 c101 * 6613 197118723 1533652571
  17:23:25.098159 udp/rtp 4 c101 * 6614 197118723 1533652571
  17:23:25.098389 udp/rtp 4 c101 * 6615 197118723 1533652571
  17:23:25.114263 udp/rtp 4 c101 * 6616 197118723 1533652571
  17:23:25.114377 udp/rtp 4 c101 * 6617 197118723 1533652571
  17:23:25.114392 udp/rtp 4 c101 * 6617 197118723 1533652571
  17:23:25.114402 udp/rtp 4 c101 * 6617 197118723 1533652571
  17:23:25.127360 udp/rtp 160 c0  6618 197119763 1533652571
  17:23:25.142563 udp/rtp 160 c0  6619 197119923 1533652571
  17:23:25.157877 udp/rtp 160 c0  6620 197120083 1533652571
  17:23:25.241723 udp/rtp 4 c101 * 6621 197120403 1533652571
  17:23:25.241751 udp/rtp 4 c101 * 6621 197120403 1533652571
  17:23:25.241766 udp/rtp 4 c101 * 6621 197120403 1533652571
  17:23:25.260182 udp/rtp 4 c101 * 6622 197120403 1533652571
  17:23:25.313686 udp/rtp 4 c101 * 6623 197120403 1533652571
  17:23:25.313708 udp/rtp 4 c101 * 6624 197120403 1533652571
  17:23:25.313721 udp/rtp 4 c101 * 6624 197120403 1533652571
  17:23:25.313728 udp/rtp 4 c101 * 6624 197120403 1533652571
  17:23:25.320545 udp/rtp 160 c0  6625 197121363 1533652571
  17:23:25.325668 udp/rtp 160 c0  6626 197121523 1533652571
  17:23:25.355376 udp/rtp 160 c0  6627 197121683 1533652571
  17:23:25.360447 udp/rtp 160 c0  6628 197121843 1533652571
  17:23:25.385616 udp/rtp 160 c0  6629 197122003 1533652571
  17:23:25.486738 udp/rtp 4 c101 * 6630 197122243 1533652571
  17:23:25.486777 udp/rtp 4 c101 * 6630 197122243 1533652571
  17:23:25.486826 udp/rtp 4 c101 * 6630 197122243 1533652571
  17:23:25.486921 udp/rtp 4 c101 * 6631 197122243 1533652571
  17:23:25.492201 udp/rtp 4 c101 * 6632 197122243 1533652571
  17:23:25.534484 udp/rtp 4 c101 * 6633 197122243 1533652571
  17:23:25.534505 udp/rtp 4 c101 * 6634 197122243 1533652571
  17:23:25.534514 udp/rtp 4 c101 * 6634 197122243 1533652571
  17:23:25.534519 udp/rtp 4 c101 * 6634 197122243 1533652571
  17:23:25.540002 udp/rtp 160 c0  6635 197123283 1533652571
  17:23:25.540155 udp/rtp 160 c0  6636 197123443 1533652571
  17:23:25.580041 udp/rtp 160 c0  6637 197123603 1533652571
  17:23:25.640075 udp/rtp 4 c101 * 6638 197123923 1533652571
  17:23:25.640106 udp/rtp 4 c101 * 6638 197123923 1533652571
  17:23:25.646655 udp/rtp 4 c101 * 6638 197123923 1533652571
  17:23:25.705011 udp/rtp 4 c101 * 6639 197123923 1533652571
  17:23:25.710230 udp/rtp 4 c101 * 6640 197123923 1533652571
  17:23:25.710259 udp/rtp 4 c101 * 6641 197123923 1533652571
  17:23:25.710286 udp/rtp 4 c101 * 6641 197123923 1533652571
  17:23:25.710301 udp/rtp 4 c101 * 6641 197123923 1533652571
  17:23:25.710313 udp/rtp 160 c0  6642 197124883 1533652571
  17:23:25.723594 udp/rtp 160 c0  6643 197125043 1533652571
  17:23:25.745100 udp/rtp 160 c0  6644 197125203 1533652571
  17:23:25.762744 udp/rtp 160 c0  6645 197125363 1533652571