Version: 1.18
PRELIMINARY/CONFIDENTIAL
TrueSpeech® Co-Processor
AGC Input level
Max AGC Gain
AGC Gain
Min AGC Gain
AGC Output level
Attack Threshold
Decay
Attack Hold
Hold
Decay
Figure 9-1:
AGC Attack Hold & Decay
The above figure illustrates the AGC Input signal level (signal envelope), the AGC Gain, and the AGC Output signal
level.
During the initial Decay phase shown, the input signal is constant at a low level. Since the AGC output level is
below the Attack Threshold, the AGC gain increases, which in turn increases the output signal level. In this
example, the gain increases until the AGC Max Gain value is reached, at which point no further increase in gain is
possible.
In the next phase, the input signal level suddenly increases, causing the output signal level to exceed the Attack
Threshold. At this point, the AGC enters the Attack Phase, and the AGC gain is decreased until the output signal
level is below the Attack Threshold.
CT8022A11AQC FW Revision 0118 DSP GROUP, INC., 3120 SCOTT BOULEVARD
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
89
All specifications are subject to change without prior notice.
ETC [ ETC ]
