About RFC 2833

RFC 2833 specifies a way of encoding DTMF signaling in RTP streams. It does not encode the audio of the tone itself, instead a signal indicates the tone is being sent. RFC 2833 defines how to carry DTMF events in RTP packets. It defines a payload format for carrying DTMF digits used when a gateway detects DTMF on the incoming messages and sends the RTP payload instead of regular audio packets.