CDB6420 Просмотр технического описания (PDF) - Cirrus Logic

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CDB6420

Full-Duplex Speakerphone Chip

Cirrus Logic 

CDB6420

RSThd - Receive Suppression speech-detection

Threshold

5 dB:

3 dB:

6 dB:

default

make disengaging receive suppression easier

(sensitive to bursty far end noise)

make receive suppression harder to disengage

(less sensitive to far end noise).

NCC - Network (echo canceller) Coefficient

Control

Normal:

Clear:

Freeze:

coefficients adapt to echo path

coefficients held to zero (no cancellation)

coefficients held to current values and adapta-

tion halted

NErle - Network ERLE threshold

24 dB:

18 dB:

30 dB:

default

network echo canceller tends to go to full-du-

plex more easily (faster)

network echo canceller requires good perfor-

mance to go to full-duplex (slower)

NFNse - Network Full-duplex Noise threshold

zero:

-42 dB:

-54 dB:

use NErle as sole criterion to transition to full-

duplex.

echo path may not exist, so go to full-duplex

when noise level is below -42 dB (easy) and in-

ternal determination of path/no path is complete

echo path may not exist, so go to full-duplex

when noise level is below -54 dB (hard) and in-

ternal determination of path/no path is complete

TVol - Transmit Volume

30 dB, 27 dB, ... , -57 dB, -60 dB, mute:

digital volume control, positive numbers are

AGC’d.

RHDet - Receive Half-duplex Detect threshold

5 dB:

3 dB:

6 dB:

default

half-duplex detects far end speech more easily

(more sensitive to far end noise)

half-duplex less sensitive to far end speech (less

sensitive to far end noise)

HHold - Half-duplex Hold on howl

checked: after howl, CS6420 remains in half-duplex

unchecked: after howl, CS6420 readapts

HDly - Half-duplex holdover Delay

200 ms:

100 ms:

150 ms:

default

very easy to break in, but may falsely switch

somewhat easy to break in, but may falsely

switch

HD - Half-duplex Disable

checked: CS6420 will never be in half-duplex.

unchecked: CS6420 can be in half-duplex as needed.

NseRmp - Noise estimator Ramp rate

1 sec:

0.5 sec:

2 sec:

noise estimator increases noise level by

3 dB/ 1 sec

estimated noise level increases by 3 dB/ 0.5 sec

(improves tracking of dynamic noise levels)

estimated noise level increases by 3 dB/ 2 sec

(improves detection of long bursts of speech)

THDet - Transmit Half-duplex Detect

threshold

5 dB:

3 dB:

6 dB:

default

half-duplex tends to detect transmit speech

more easily (more sensitive to near end noise)

half-duplex is less sensitive to transmit speech

(less sensitive to near end noise)

RVol - Receive Volume

30 dB, 27 dB, ... , -57 dB, -60 dB, mute:

digital volume control where positive numbers

are AGC’d

ACC - Acoustic (echo canceller) Coefficient

Control

Normal:

Clear:

Freeze:

coefficients adapt to echo path

coefficients held to zero (no cancellation)

coefficients held to current values and adapta-

tion halted

AErle - Acoustic ERLE threshold

24 dB:

18 dB:

30 dB:

default

acoustic echo canceller tends to go to full-du-

plex more easily (faster)

acoustic echo canceller requires good perfor-

mance to go to full-duplex (slower)

DS205DB1

47

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