Version: 1.18
PRELIMINARY/CONFIDENTIAL
TrueSpeech® Co-Processor
Example: Telephone Echo environment (local 2-to-4 wire hybrid provides 20+ dB or cancellation - small amplitude
echoes).
C1
S1
C2
S2
E011H
E011H
0100H
0100H
Set NLP threshold floor
Use higher threshold floor value
C1
S1
C2
S2
E013H
E013H
0600H
0600H
Set Attenuation Scaling/Boost
Set attenuation boost to 6dB
C1
S1
C2
E012H
E012H
0004H
Train & Lock Command
NLP threshold = Speaker Output >> 4 (divided by 16)
NLP Mode = 0, activate NLP/AS based on measured speech direction
S2
0004H
C1
S1
C2
S2
E014H
E014H
0003H
0003H
Set lock threshold (used to activate NLP/AS)
Set threshold to 3dB measured attenuation
For low-level echoes, it is recommend that the NLP activation mode be set to 0, since for low-level input echoes the
AEC may not be able to accurately measure the achieved AEC cancellation. Activating the NLP/AS/AB using the
sensed speech direction will often produce better results.
Increasing the NLP threshold floor and reducing the NLP Threshold Scaling can often produce increased echo
attenuation. It can also increase the AS or AB values.
Use of NLP activation mode 1 (use measured AEC attenuation to enable NLP/AS/AB) will tend to produce better
full-duplex operation at the expense of reduced echo attenuation.
CT8022A11AQC FW Revision 0118 DSP GROUP, INC., 3120 SCOTT BOULEVARD
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
111
All specifications are subject to change without prior notice.
ETC [ ETC ]
