W681307 Datasheet, PDF (89/160 Pages) Winbond – USB1.1 CODEC Microprocessor Control Unit with 32KB Mask ROM and 4KB RAM

W681307
13. ECHO CANCELLER
13.1
Half AEC Block Diagram
The acoustics echo cancellation unit removes the echo signal inserted by the speaker and space.
Figure 13-1 illustrates the block diagram of the Half Acoustics Echo Canceller in the Speech Processor.
Figure 13-1 The signal flow through the Acoustics Echo Canceller in the Speech Processor
13.1.1
Acoustics Suppression
When enabled (and so, switched into the network output data path) the acoustic suppression unit will insert a configurable attenuation
factor into the network output path. The attenuation will switch between a maximum and minimum value depending on the presence or
absence of speech on the network output data path. When speech is present the attenuation will converge towards the minimum value.
When speech is absent the attenuation will converge towards the maximum value. The attenuation factor will not switch abruptly between
these two factors but will exponentially converge from one to the other.
： When enabled the network output data path will include the following arithmetic unit
Nout ∝ Nout ∗ AS _ ATTENUATION
- 89 -
Publication Release Date: May, 2007
Revision 1.3