BM28723AMUV
14.6 3 Band DRC - continued
DRC transition figure
Input
A_TIME
AGC_TH
Volume
Level
Output
AGC_TH
R_TIME
R_TIME
A_RATE
R_RATE
A_TIME
In here A_TIME is the time for detecting time before gain starts to decrease. And A_RATE decides the slope of gain
compression.
On the other hand, R_TIME is the time for detecting before starting to release gain operation. And R_RATE decides slope
of release gain.
Figure 58
DRC1, DRC2, DRC3 can be set 2 types of threshold (AGC_TH1 and AGC_TH2) as shown below. If output is in between
AGC_TH1 and AGC_TH2, a slant for output gain can be made. If input become bigger and output over AGC_TH2, output
gain doesn’t have slant and become constant level. Slope setting (α) is calculated by AGC_TH1, AGC_TH2 and the value
of input gain to DRC block for reaching AGC_TH2 (xdB).
The operation between AGC_TH1 and AGC_TH2 is named as DRC1slope and DRC2slope and DRC3slope
.
And the operation over AGC_TH2 is named as DRC1comp and DRC2comp and DRC3comp
.
Each operation can be set ON/OFF, A_TIME, A_RATE, R_TIME, R_RATE respectively.
For example, DRC1 do not have slope curve when setting DRC1slope OFF and DRC1comp ON.
DRC4 can be set only AGC_TH2 therefore DRC4 do not have slope function.
DRC input-and-output gain characteristics
[dB]
VO
The formula which asks for Slope α is described below.
α changes into 8bit Hex data of the complement of 2 the value
α =0x00
calculated by calculation.
102y0 102x0
α
AGC_TH2
y=-6dB
128
10TH 102x0
20
AGC_TH1
-12dB
α =0x80
TH is AGC_TH1. x is input level. y is output level.
Ex) It asks for α at the time of AGC_TH1 = -12dB, x = 0dB y = -6dB
106 10200
Slope function Compressor
Area Area
20
128
102102 10200
85 .266
VOinf
→ 0x55
0x55calculated is setto command0x29, 0x31 or 0x39.
-12dB
x=0dB
VIinf
VI
Figure 59
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31.Aug.2018 Rev.001
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