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When using an output channel as a reference, the reference point is post volume control;
therefore, changes to the listening volume in the room will affect the AEC gain structure
(see “AEC Dialog” on page43). If you have an output channel on the DMP128 that
is not being used, you can isolate the reference channel from the channel being used for
volume control by routing reference signals to the unused output channel.
Alternately, if you do want the reference signal to track with changes in listening volume,
yet want more control over the actual reference level:
a. Route the far end signal to both the amplifier output and the virtual (unused)
output.
b. Create a group master control that contains the amplifier output and virtual
output. Set soft limits for the group master control, as desired.
c. Set optimal level for the amplified output. Set optimal level for virtual output.
Relative levels between both settings will be maintained by using the group
master control.
AEC Configuration
To insert and configure an AEC processor:
1. Insert an AEC processor on the desired input channel using one of the following
methods:
• Double-click the AEC (filter) block in the DSP Configurator workspace.
• Right-click the AEC block to open the context menu and select Insert AEC.
• Click the AEC block to select it (or use the arrow keys to navigate to the AEC
block) and press the <Enter> key on your keyboard.
2. Double-click the AEC processor to open it. Open the Select Reference drop-down list
and select a reference.
3. Click the Bypass button to disengage bypass. The AEC processor is now operational.
AEC Dialog
The AEC dialog contains a number of meters and indicator LEDs
that are essential for setting up gain structure and monitoring activity.
The AEC reference must be selected from a list, otherwise the
echo canceller will not work. Noise Cancellation, part of the AEC
processor, is selected and adjusted here. A detailed description of
the AEC dialog components is included below.
Activity LEDs
• Far – lights when activity is detected from the remote site.
• Near – lights when activity is detected from the local site.
• Update – lights when the SEC is updating, i.e., converging or
reconverging.
DMP128 • Software Control 43