Automatic Gain Control (Agc) - AudioCodes Mediant 4000 SBC User Manual

14.6

Automatic Gain Control (AGC)

Automatic Gain Control (AGC) adjusts the energy of the output signal to a required level
(volume). This feature compensates for near-far gain differences. AGC estimates the
energy of the incoming signal from the IP, determined by the 'AGC Redirection' parameter,
calculates the essential gain, and then performs amplification. Feedback ensures that the
output signal is not clipped. You can configure the required Gain Slope in decibels per
second using the 'AGC Slope' parameter and the required signal energy threshold using
the 'AGC Target Energy' parameter.
When the AGC first detects an incoming signal, it begins operating in Fast Mode, which
allows the AGC to adapt quickly when a conversation starts. This means that the Gain
Slope is 8 dB/sec for the first 1.5 seconds. After this period, the Gain Slope is changed to
the user-defined value. You can disable or enable the AGC's Fast Mode feature, using the
ini file parameter AGCDisableFastAdaptation. After Fast Mode is used, the signal should
be off for two minutes in order to have the feature turned on again.
The following procedure describes how to configure AGC using the Web interface:

To configure AGC using the Web interface:
1. Open the DSP Settings page (Setup menu > Signaling & Media tab > Media folder >
DSP Settings):
2. Configure the following parameters:
•
'Enable AGC' (EnableAGC) - Enables the AGC mechanism.
•
'AGC Slope' (AGCGainSlope) - Determines the AGC convergence rate.
•
'AGC Redirection' (AGCRedirection) - Determines the AGC direction.
•
'AGC Target Energy' - Defines the signal energy value (dBm) that the AGC
attempts to attain.
•
'AGC Minimum Gain' (AGCMinGain) - Defines the minimum gain (in dB) by the
AGC when activated.
•
'AGC Maximum Gain' (AGCMaxGain) - Defines the maximum gain (in dB) by the
AGC when activated.
•
'AGC Disable Fast Adaptation' (AGCDisableFastAdaptation) - Enables the AGC
Fast Adaptation mode.
3. When
(TranscodingMode) parameter must be set to Force. The parameter can either be the
global parameter or per IP Profile.
4. Click Apply.
User's Manual
Figure 14-12: AGC Parameters
using AGC with the SBC application,
204
Mediant 4000 SBC
the 'Transcoding Mode'
Document #: LTRT-42025