rfc4733- DTMF is sent out of band of the main audio stream. This supercedes the older RFC-2833 used within the older
inband- DTMF is sent as part of audio stream.
info- DTMF is sent as SIP INFO packets.
auto- DTMF is sent as RFC 4733 if the other side supports it or as INBAND if not.
auto_info- DTMF is sent as RFC 4733 if the other side supports it or as SIP INFO if not.
This documentation was imported from Asterisk Version GIT-13-13.15.0-rc1-262276-g507ce0ag1f59d08