User Manual

Cisco High-Density Analog Voice and Fax Network Module
Configuration Tasks
20
Cisco IOS Release 12.2(2)XT and 12.2(8)T
Voice Quality Tuning Commands
The commands in this section configure parameters to improve voice quality. Common voice quality
issues include the following:
• Configuring Adaptive Jitter Adjustment (optional)
• Configuring Echo Adjustment (optional)
• Configuring Voice Level Adjustment (optional)
Configuring Adaptive Jitter Adjustment
To configure the playout delay jitter buffer, use the following commands beginning in dial-peer or
voice-port configuration mode:
Command Purpose
Step 1
Router(config-voiceport)# playout-delay mode {adaptive
| fixed}
Determines the mode in which the jitter buffer will
operate for calls on this voice port.
The keywords are as follows:
• adaptive—Adjusts the jitter buffer size and
amount of playout delay during a call based on
current network conditions.
• fixed—Defines the jitter buffer size as fixed so
that the playout delay does not adjust during a
call. A constant playout delay is added.
The default is adaptive.
Step 2
Router(config-voiceport)# playout-delay {nominal value
| maximum value | minimum {default | low | high}}
Tunes the playout buffer to accommodate packet
jitter caused by switches in the WAN.
The keywords and arguments are as follows:
• nominal—Defines the amount of playout
delay applied at the beginning of a call by the
jitter buffer in the gateway. In fixed mode, this
is also the maximum size of the jitter buffer
throughout the call.
• value—Specifies the range that depends on
type of DSP and configured codec complexity.
For medium codec complexity, the range is
from 0 to 150 ms. For high codec complexity
and DSPs that do not support codec
complexity, the range is from 0 to 250 ms.
• maximum (adaptive mode only)—Specifies
the jitter buffer's upper limit (80 ms), or the
highest value to which the adaptive delay is set.
• minimum (adaptive mode only)—Specifies
the jitter buffer's lower limit (10 ms), or the
lowest value to which the adaptive delay is set.
• default—Specifies 40 ms.