poolek
join:2003-11-04
Austin, TX
 ·RoadRunner Cable
 ·AT&T U-Verse
 ·ViaTalk
 ·AT&T Yahoo
| reply to bbrookfield
Re: [ViaTalk] Partial fix for DTMF issue
I'm not an expert on this stuff, so what I say may be wrong - but this is what I understand from reading stuff...
When you press a button on the phone, it generates the DTMF tone that is sent to the PAP2.
If you have INBAND, nothing is done. The PAP2 passes the DTMF tone through the codec just like any other sound. This tends to work ok with high quality codecs. With codecs that use more compression, the DTMF sound ends up being too distorted to work.
If you have one of the out-of-band options set, the PAP2 recognizes the DTMF tone and sends a signal outside of the codec that indicates which button was pressed. Somewhere on the VOIP server side, the system gets this code then regenerates the DTMF code. This prevents the compression from the codec from messing up the DTMF sound. Somewhere in there, the DTMF sound that's generated by the phone itself is supposed to be muted. I don't know if that occurs at the adaptor or server-side. Where ever it occurs, that's where VT's implementation fails. The first DTMF tone you hear is from your phone handset. The second is the regeneration from VT's server.
I would -guess- that VT VM system isn't 'listening' for DTMF codes, instead it's looking for the out-of-band signals. That's why it doesn't work when you set the adaptor to 'INBAND'. Every other IVR out there would just listen for the tones since they wouldn't have access to the out of band stuff. So, INBAND works with everything else because it doesn't introduce duplication due to the lack of muting, and the codec VT uses is high enough quality to accurately replicate the tone.
Theoretically, you could access VT voicemail with INBAND if you're calling in from any VOIP other provider because VT's voicemail interface to the 'outside' world would be listening for DTMF, not looking for the out of band stuff. It just doesn't work when you're calling from your own VT line.
FWIW - I have the updated firmware and still have issues with DTMF. I firmly believe I'll continued to have issues until the muting issue is resolved (don't know if that's a VT issue or a PAP2 issue), or VT changes their VM to also listen for INBAND DTMF. |
