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5.4 Using the Energy Detector
AG boards are capable of running an energy detector which examines the inband signal, distinguishing between silence and energy. The energy detector generates the following events:
A
DIEVN_SILENCE_DETECTED
ADIEVN_ENERGY_DETECTED
ADIEVN_ENERGY_DETECT_DONE
You can manually start or stop the energy detector using these functions:
To...
Use ...
Start the energy detector
adiStartEnergyDetector
Stop the energy detector
adiStopEnergyDetector
5.4.1 Energy Detection Parameters
adiStartEnergyDetector
takes two qualification time parameter arguments:
energyqual
- The time in milliseconds in which energy must be present to report an energy event.
silencequal
- The time in milliseconds in which energy must not be present to report a silence event.
Additional energy detector parameter information is stored in the
ADI_ENERGY_PARMS
structure, which is defined in the
AG Access Function Reference Manual
.
You can modify the energy detector's default behavior by specifying the following arguments when invoking
adiStartEnergyDetector
:
thresholdampl
-The noise level in dBm, below which is considered silence. Noise above this level is further qualified as energy.
deglitch
-The minimum time in milliseconds before a transition between energy and silence is recognized.
autostop
- Controls whether the energy detector continues running after the first event. By default, automatic stop is enabled.
Figure 15
illustrates the energy detection parameters stored in
ADI_ENERGY_PARMS
:
Figure 15. Energy Detection Parameters
5.4.2 Terminating Energy Detection
The
adiStopEnergyDetector
function immediately terminates energy/silence detection. AG Access generates an
ADIEVN_ENERGYDETECT_DONE
event with the value set to
CTA_REASON_STOPPED
, which means that the operation was stopped by application request.
AG Access may also generate the
ADIEVN_ENERGYDETECT_DONE
event with an error code,
ADIERR_xxx
or
CTAERR_xxx
, or with the value set to
CTA_REASON_FINISHED
. When set to
autostop
(one-shot), the value is set to
CTA_REASON_FINISHED
and the
size
field contains either
ADIEVN_ENERGY_DETECTED
or
ADIEVN_SILENCE_DETECTED
.
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(Page 5 of 8 in this chapter)
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