I have having trouble with both missing and duplicated DTMF in Freeswitch. 

Here are the steps of how I am using it:

1. Leg A - I am calling out from my Freeswitch instance (through iCall), and I am calling an iCall number that is also connected to the same Freeswitch instance. 

2. Leg B - The above call is routed through iCall and then answered by the same Freeswitch instance. 

3. On Leg B, I play a file and attempt to get DTMF in a lua script. Here is the code of interest:

callPin = session:playAndGetDigits(1, 10, 4, 30000, "#","/tmp/cw_17.wav", "", "\\d+");


4. On Leg A, I send DTMF information in a lua script. Here is the code of interest. I initiate a delay between each digit:

local newPin = "";

for i = 1, string.len(pin) do

  newPin = newPin .. string.sub(pin, i, i) .. "W";

end

session:execute("send_dtmf", newPin .. "#@200");


** Note that there is a session:sleep on Leg A before I send the DTMF to make sure i don't send it too early **


The problem is that the recognized DTMF on Leg B is wrong about 30% of the time. For example, if Leg A enters: 22063083, Leg B will get the DTMF digits 222063083. This is an example of duplication, but I have also experienced missing DTMF codes (and an occasional wrong code completely) 


I have messed with a bunch of DTMF settings in hopes of fixing this issue, but I cannot seem to find something that is reliable 100% of the time.


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Here are the DTMF settings I have looked at / messed with. I've tried various values for the dtmf-duration in the config (and in the send_dtmf command above)


    <!-- This is in external.xml -->

    <param name="dtmf-duration" value="500"/>

    <param name="dtmf-type" value="rfc2833"/>

    <param name="inbound-codec-prefs" value="$${global_codec_prefs}"/>

    <param name="outbound-codec-prefs" value="$${outbound_codec_prefs}"/>

    <param name="inbound-codec-negotiation" value="greedy"/>

    <!-- This is in vars.xml -->
    <X-PRE-PROCESS cmd="set" data="global_codec_prefs=PCMU"/>
    <X-PRE-PROCESS cmd="set" data="outbound_codec_prefs=PCMU"/>

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I have run fs_cli with event logging and the DTMF events that Freeswitch gets do correlate to the wrong value (e.g. the duplication / missing digits is noticable in the Freeswitch events as well). 

Also, I am not running any dtmf-related applications on the session before I give control to the lua scripts (e.g. not running start_dtmf)

Has anyone experienced this type of issue? Or know what I can do to resolve it? My next step was going to be trying this against another provider besides iCall, but I figured I would see if anyone has encountered a similar problem before. Any help is appreciated.

Thanks