Version: 1.18
PRELIMINARY/CONFIDENTIAL
TrueSpeech® Co-Processor
9.15.1
Concurrent AEC and Speech Operation
Speakerphone
volume
Playback
volume
control
Speech
Decoder
Playback
Buffer
vox
Echo
control
Host
Interface
AEC
Suppressor
Record
volume
control
Speech
Encoder
Record
Buffer
Advanced
AEC
Processing
vox
DTMF and Tone
Detection
Figure 9-3:
AEC and Speech Compression
Figure 9-3 shows the relationship of the Speakerphone Acoustic Echo Canceller (AEC) and Echo Suppressor
components to the record/playback channels when DSVD Speakerphone mode is used.
Note that the VOX detectors at the Echo Suppressor inputs make the decision regarding Echo Suppressor speech
direction. Changes to the playback level made through the playback volume control (recommended) will be detected
by the VOX and affect the direction decision. Changes to the playback level made through the Speakerphone
volume control (Set Speakerphone Parameters command) will not be detected by the VOX and will not affect the
direction decision.
When removing playback echoes at the Tone Detector inputs only (and speech compression/record is not used)
through the AEC, set the Echo Suppressor (loop attenuation) 0dB, disable the automatic loop adjust mode, and set
the Advanced AEC feature to Off:
1. Enable AEC
2. Disable Advanced AEC
3. Enable DTMF and/or Tone Detectors
4. Start playback
5. Set loop attenuation to 0dB
6. Switch automatic loop adjustment off
7. Set loop attenuation to 0dB (to force removal of any attenuation added by the auto loop adjustmet mode)
Once this combination of features has been set up, you may stop and restart playback without reprogramming
the AEC.
CT8022A11AQC FW Revision 0118 DSP GROUP, INC., 3120 SCOTT BOULEVARD
SANTA CLARA, CA 95054 PH: 408 986 – 4300 FAX: 408 986 – 4490
101
All specifications are subject to change without prior notice.
ETC [ ETC ]
