User`s guide

Configuring MultiVoice
MultiVoice configuration examples
MultiVoice Gateway for the MAX— User’s Guide Preliminary November 23, 1998 6-13
This parameter defaults to 2. This parameter is ignored if the Packet Audio Mode
parameter is set to G.723.
Note: For certain MultiVoice Gateway configurations, dynamic jitter buffer support is not
available. Table 6-2 summarizes those configuration items which affect jitter buffer operations.
Determining jitter buffer size
The dynamic jitter buffer size is a function of the following:
• The RTP packet duration (in milliseconds) for the selected audio codec,
• The number of RTP packets defined for the jitter buffer.
The dynamic jitter buffer size is determined by multiplying the number of RTP packets entered
for the initial and maximum jitter buffer parameters and packet duration, the total speech in
milliseconds contained in one RTP packet:
For example, in fixed mode, if the Initial Jtr Buf Size=5, and an in-coming call used the G.711
codec with one audio frame per packet, and has a packet duration of 5ms, then:
5 (Packets) x 5ms/packet = 25ms (jitter buffer length)
The instantaneous jitter buffer size within the call is 25ms. If a second in-coming call used the
G.729(A) codec, and had five audio frames per packet, with a packet duration of 50ms, then
the instantaneous jitter buffer size within this call would be 250ms.
Table 6-3 and Table 6-4 contain the supported per call jitter buffer lengths:
Table 6-2. Configuration dependencies affecting jitter buffer processing
Configured mode Enable Adaptive Jtr Buf Max Jtr Buf Size Initial Jtr Buf Size
Pkt Audio Mode=G.723 N/A N/A N/A
Silence Detect/CNG=Yes N/A N/A Active
Fixed Jtr Buf Mode No N/A Active
Adaptive Jtr Buf Mode Yes Active Active
Initial Jtr Buf Size x Packet Duration (ms)
Max Jtr Buf Size x Packet Duration (ms)
Table 6-3. Jitter buffer length (in milliseconds) for the G.711 audio codec
Jitter
a
buffer
packets
Packet duration (ms), for one to 10 audio frames per RTP packet using the G.711 codec
1 frame
@5ms
2 frames
@10ms
3 frames
@15ms
4 frames
@20ms
5 frames
@25ms
6 frames
@30ms
7 frames
@35ms
8 frames
@40ms
9 frames
@45ms
10 frames
@50ms
1 51015202530354045 50
2 10 20 30 40 50 60 70 80 90 100