[Freeswitch-users] Serious and urgent problem with DTMF! Please help...

[Dennis]

hi all,

thanks a lot for your support!

the codec we are using is G711a, so normally using inband should work.
no transcoding is done. we get G711, fs works with G711 and G711
leaves our servers.
although the only short way, we are using voip is a 10 meter long CAT7
wire connected to a cirpack, we would prefer to use rfc-2833 for
signaling dtmf inputs.

the dtmf detector is off.

we spoke to someone from the cirpack-support and he told us, that they
do not filter the inband tone, if G711 is used, because we do not need
rfc-2833 when using G711. if a lower quality codec is used (like
G729), cirpack will filter the inband tone and send rfc-2833 instead.


we have the following scenarios:

1.) we set dtmf to "info":

cirpack sends us a clean tone and fs sees one clean tone (both: ||||||||||)

conclusion: we could drop rfc-2833 and only use inband.


2.) we set dtmf to "rfc-2833":

cirpack send us the tone with a tiny gap (2ms) and rfc-2833 (||
|||||||||). the guy from cirpack told us, that this is not a real gap,
but only wireshark sees it as a gap. the gap is where cipack adds the
requested rfc-2833 information.
but, fs hears the inband tone as if it were 2 tones and the rfc-2833.
this worked for us before, because we only reacted on the rfc-2833
signal.
now we have to send the audio to another side. on the other side the 2
inband (one splitted) tones are heard, which leads to problems.


under the following url you can see a screenshot taken from wireshark.
the first row is, how cirpack sends the inband and rfc-2833. to last
row shows, how fs sees the tone.
https://photos-1.dropbox.com/i/o/uy03PGj0ZEtxIi3r7RV9dBkXXvRoxmJ-KlcBi1i9ovg/3475265/1282986000/8a42bd3


are there some timing-settings in fs, we could play with to make the
tiny gap dissaper or something like that, or should we just switch
completely to inband?


thanks
dennis