Medias Mediatrix 1204, Справочное руководство

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Voice & Fax Codecs Reference Manual (SIP Version)
Mediatrix 1204 83
• g726-40kbps
The default value is pcmu .
4. Enable the jitter buffer protection by selecting Enable in the Adaptive Jitter Buffer choice.
The jitter buffer allows better protection against packet loss, but increases the voice delay. If the
network to which the Mediatrix 1204 is connected suffers from a high level of congestion, the jitter
buffer protection level should be higher. If the network to which the Mediatrix 1204 is connected
suffers from a low level of congestion, the jitter buffer protection level should be lower.
5. Define the target jitter buffer length in the Target Jitter Buffer field.
The adaptive jitter buffer attempts to hold packets to the target holding time. This is the minimum
delay the jitter buffer adds to the system. The target jitter buffer length is in ms and must be equal
to or smaller than the maximum jitter buffer.
Values range from 0 ms to 300 ms. The default value is 30 ms. You can change values by
increments of 1 ms, but Mediatrix recommends to use multiple of 5 ms.
It is best not to set target jitter values below the default value. Setting a target jitter buffer below 5 ms
could cause an error. Jitter buffer adaptation behaviour varies from one codec to another. See
“About Changing Jitter Buffer Values” on page 84 for more details.
6. Define the maximum jitter buffer length in the Maximum Jitter Buffer field.
This is the maximum jitter the adaptive jitter buffer can handle. The jitter buffer length is in ms and
must be equal to or greater than the target jitter buffer.
Values range from 0 ms to 300 ms. The default value is 125 ms. You can change values by
increments of 1 ms, but Mediatrix recommends to use multiple of 5 ms.
See “About Changing Jitter Buffer Values” on page 84 for more details.
7. Set the DTMF transport type in the DTMF Transport field.
The following choices are available:
Table 52: 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.
outOfBandUsingSignalingProtocol The DTMFs are transmitted as per draft-choudhuri-sip-info-
digit-00.txt .
Note : This feature and the Hook Flash processing feature
via signalling protocol are totally independent. Activating
one of these features has no effect on the other. See
“Hook
Flash Processing” on page 256 for more details.
signalingProtocolDependent The signalling protocol has the control to select the DTMF
transport mode. The SDP body includes both RFC 2833
and
draft-choudhuri-sip-info-digit-00.txt in that order of
preference.
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 1204
receives and sends out-of-band DTMFs as per RFC 2833 using RTP. DTMFs supported are 0-9, A-D, *, #.