[asterisk-dev] Clipped DTMF on Zap Channel - 1.4-r93000 - VLDTMF Incompatibility?

[Gregory Boehnlein]

Hello,
	I'm running into an issue that should be simple to correct, but I
must be overlooking something in my troubleshooting. The situation is that I
have an Asterisk 1.4 server sitting in front of a Shoretel PBX acting as a
Media Gateway to convert SIP to PRI. I take SIP channels into the Asterisk
server, conver them to PRI and push them into the Shortel box. However,
inbound DTMF is getting clipped on the Zap channel. I have enabled dtmf
debugging and I can see the DTMF events being generated by the SIP side;

[Dec 16 07:38:53]     -- Zap/25-1 is proceeding passing it to
SIP/ocpm-mg-10beab20
[Dec 16 07:38:53]     -- Zap/25-1 is ringing
[Dec 16 07:38:53]     -- Zap/25-1 answered SIP/ocpm-mg-10beab20
[Dec 16 07:38:57] DTMF[3259]: channel.c:2441 __ast_read: DTMF begin '4'
received on SIP/ocpm-mg-10beab20
[Dec 16 07:38:57] DTMF[3259]: channel.c:2451 __ast_read: DTMF begin
passthrough '4' on SIP/ocpm-mg-10beab20
[Dec 16 07:38:57] DTMF[3259]: channel.c:2378 __ast_read: DTMF end '4'
received on SIP/ocpm-mg-10beab20, duration 100 ms
[Dec 16 07:38:57] DTMF[3259]: channel.c:2419 __ast_read: DTMF end accepted
with begin '4' on SIP/ocpm-mg-10beab20
[Dec 16 07:38:57] DTMF[3259]: channel.c:2435 __ast_read: DTMF end
passthrough '4' on SIP/ocpm-mg-10beab20
[Dec 16 07:38:58] DTMF[3259]: channel.c:2441 __ast_read: DTMF begin '4'
received on SIP/ocpm-mg-10beab20
[Dec 16 07:38:58] DTMF[3259]: channel.c:2451 __ast_read: DTMF begin
passthrough '4' on SIP/ocpm-mg-10beab20
[Dec 16 07:38:58] DTMF[3259]: channel.c:2378 __ast_read: DTMF end '4'
received on SIP/ocpm-mg-10beab20, duration 100 ms
[Dec 16 07:38:58] DTMF[3259]: channel.c:2419 __ast_read: DTMF end accepted
with begin '4' on SIP/ocpm-mg-10beab20
[Dec 16 07:38:58] DTMF[3259]: channel.c:2435 __ast_read: DTMF end
passthrough '4' on SIP/ocpm-mg-10beab20
[Dec 16 07:39:01]     -- Hungup 'Zap/25-1'
[Dec 16 07:39:01]   == Spawn extension (default, 2162313300, 1) exited
non-zero on 'SIP/ocpm-mg-10beab20'
[Dec 16 07:39:02] Really destroying SIP dialog
'2c07781034b7db7d67cea3532706e718 at 207.166.192.174' Method: BYE

However, when I do a Ztmonitor, I can hear only a 1 or 2 ms DTMF tone.

Now.. the system that is sending the SIP packets to the 1.4 box is an
Asterisk 1.2 box. What I assume is happening is that the 1.2 system is
sending the old style rapid fire DTMF events, and the Asterisk 1.4 box is
processing them in the way that a sane RFC-2833 gateway would and starting
the DTMF, then immediately ending it upon receipt of the "end of event"
marker.

I can provide the Ztmonitor scans and packet traces if anyone likes..