DISA - DTMF not recognize via Google Voice

I have Asterisk 1.6.1.4, with DISA via SIP DID line. However, when using it with my Google Voice call forwarding to the same SIP DID, the DISA does not work; it always timeout after TIMEOUT(response) as if it did not see the DTMF.

This is the call flows -
For Google Voice forwarded calls - caller -> Google Voice -> SIP DID -> Asterisk
For Direct dialed calls - caller -> SIP DID -> Asterisk.

From the Asterisk both calls came from the same SIP provider.

From the wireshare trace, both calls show RFC2833 RTP events with proper dialed number; the only difference for Google Voice forwarded calls, it has the “volume:3” vs “volume:10” in a direct dialed; also the 2833 event repeated 9 times in Google Voice, vs 10 times for direct dialed.

This problem seems only in DISA applications; I change the dialplan and have WaitExten instead. It got the DTMF correctly in both cases.

Am I missing something here ?

Thanks in advanced.

[quote=“zilla1k”]I have Asterisk 1.6.1.4, with DISA via SIP DID line. However, when using it with my Google Voice call forwarding to the same SIP DID, the DISA does not work; it always timeout after TIMEOUT(response) as if it did not see the DTMF.

This is the call flows -
For Google Voice forwarded calls - caller -> Google Voice -> SIP DID -> Asterisk
For Direct dialed calls - caller -> SIP DID -> Asterisk.

[/quote]

After some more search, I found the issue.
The problem is caused by the Google Voice recording feature, which will trigger by entering “4”.
http://www.google.com/support/forum/p/voice/thread?tid=65de915f8d7a971f&hl=en