[Asterisk-Users] Low Bit Rate Codecs

[Steve Underwood]

Hi,

DTMF will not pass reliably through *any* low bit rate codec, with the 
exception of some forms of ADPCM. GSM certainly does not work. When a 
VoIP system is configured properly it works just like a cellular 
telephone system, which suffers the same problem. It doesn't send the 
DTMF tones. It sends a message to the far end saying "outdial a digit X 
for me, please". In this way any low bit rate codec will work solidly 
for DTMF with a VoIP system.

Regards,
Steve


Dr. Rich Murphey wrote:

>If you take into consideration the need to pass DTMF to/from various SIP
>providers, how do they rank?
>
>I'd given up on g729 completely because none of the dtmfmode options seemed
>to work with g729 for several sip service providers.  GSM seems to work fine
>in general.
>  
>