Specifications

DTMF Transport Type Reference Manual (MGCP/NCS Version)
Mediatrix 4100
139
2. Restart the Mediatrix 4100 so that the changes may take effect.
DTMF Transport Type
You can define how to transport the DTMFs.
 To set the DTMF transport type:
1. In the voiceIfMIB, set the DTMF transport type in the voiceIfDtmfTransport variable
(voiceIfDtmfTransportTable group).
The following choices are available:
G.729
voiceIfCodecG729MinPTime Shortest packetization period allowed for the
G.729 codec. Authorized values start at 10 ms
and come in discrete steps of 10 ms up to the
one specified by the
voiceIfCodecG729MaxPTime variable.
Default Value: 10
10-100, with increments
of 10
voiceIfCodecG729MaxPTime Longest packetization period allowed for the
G.729 codec. Authorized values go up to
100 ms, in discrete steps of 10 ms, and start at
the one specified by the
voiceIfCodecG729MinPTime vartiable.
Default Value: 100
10-100, with increments
of 10
Table 100: Packetization Time Settings (Continued)
Variable Definition Values (ms)
Standards Supported • ITU-T Recommendation Q.24 : Multifrequency push-button
signal reception
• RFC 2833: RTP Payload for DTMF Digits, Telephony Tones
and Telephony Signals
DTMF out-of-band
Certain compression codecs such as G.723.1 and G.729 effectively distort voice because they lose
information from the incoming voice stream during the compression and decompression phases. For
normal speech this is insignificant and becomes unimportant. In the case of pure tones (such as DTMF)
this distortion means the receiver may no longer recognize the tones. The solution is to send this
information as a separate packet to the other endpoint, which then plays the DTMF sequence back by re-
generating the true tones. Such a mechanism is known as out-of-band DTMF. The Mediatrix 4100
receives and sends out-of-band DTMFs as per ITU Q.24. DTMFs supported are 0-9, A-D, *, #.
Table 101: DTMF Transport Type Parameters
Transport Parameter Description
inBand The DTMFs are transmitted like the voice in the RTP
stream.
outOfBandUsingRtp The DTMFs are transmitted as per RFC 2833 (see “
DTMF
Payload Type” on page 140 for additional information).