8169 Datasheet, PDF (14/30 Pages) STMicroelectronics – DIGITAL AUDIO PROCESSOR WITH MULTICHANNEL DDX™

STA304A
9.0 BASS MANAGEMENTAND EQ
The STA304A has the ability to redirect the sound to the SBW channel and to pass each channel through a 4-
stage cascaded 2nd order IIR filter. With the combination of the DDX gain/compressor (CRA register bits 2-3)
a dynamic EQ can be implemented. Beside that, a special Side-Firing sound can be achieved by enabling this
feature available with the ready made filter topology on the surround channels.
9.1 Bass Redirection
Figure 8.
L
C ^(*)
R
LS
RS
Phantom
Scale
RS
Scale
LS
Scale
R
Scale
C
Scale
L
LR Filter
L
(IIS C)
LR Filter
R
Sur Filter
LS
Sur Filter
RS
(*)
LFE
Scale
LFE
+
SBW
Filter
SBW
There is an option to redirect each input channel to the SBW output channel. The Scale factor of each channel
should be set with values in the range of 0 (no redirection) to -1 (full redirection). About setting the scaling factors
registers, see paragraph 10.
The redirection is taking place when the bit 0 of the Bass Management Register (add.72h) is set (see section
12.13).
Together with the static EQ option (following section), by setting appropriate filters, a full bass management so-
lution is available.
(*) Note: C and LFE channels are available only with 6 channels AC97 input. In case of 4 channels I²S, only L, R, LS, RS are
available
9.2 Static EQ
Figure 9.
Input
Scale in
Factor
bi-quad0
bi-quad1
bi-quad2
bi-quad3
Output
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