DTMF (Dual Tone Multi Frequency) is a type of signaling used primarily in voice telephony systems. It features audible tones in the frequency range of the human voice which are typically used when dialing a call (on analog lines) or when operating an IVR menu. There are many other applications for this signaling. For more information, see the wikipedia article on DTMF ( http://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling ) DTMF RTP: A dtmf packet is 16 bytes. DTMF data = 12 bytes (RTP header) + 4 bytes (RTP payload) 4 bytes (RTP payload) has mapping of key press value as event. After parsing this 4 bytes the receiver end can get instruction or event what to do. DTMF SDP: dtmf payload is 101 . It is passed on audio level of lync SDP. m=audio 5476 RTP/AVP 101 . . . a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-16 a=fmtp:101 0-16 indicates the key value that is supported...
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