Related specifications
RFC 4733, RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals, available at http://www.ietf.org/
Implementation notes
Support is provided for:
Out-of-band DTMF sending. (RFC 4733)
RTP payload format for named telephone events (Chapter 2, RFC 4733) with full support for specified DTMF events (Section 3.2, RFC 4733).
In-band DTMF playback.
Support is not provide for:
RTP Payload Format for Telephony Tones. (Chapter 4, RFC 4733.)
Out-of-band DTMF playback at the receiving end.
In-band DTMF sending.