Dsp (Digital Surround Processor) Ic - Toshiba CN27E90 Technical Training Manual

5. DSP (Digital Surround Processor) IC

Input signal entered into analog input pin 4 of DSP IC QD03
(YM7128B) is converted to 14 bit digital signal with the
sampling frequency 23.6 kHz by A/D converter of 14 bit
floating system, and enters digital delay circuit through
digital attenuator VM and doubler.
The digital delay circuit has nine output taps, and the delay
time of each tap can be controlled independently, also each
tap position can be switched by T0 to T8 register.
In a minute, the T0 output passes through the primary FIR
(Finite Impulse Response) type low pass filter, and reduction
Mode
-VM (IN)
VL (LO)
VR (RO)
VC (Echo)
GL1
2
3
4
5
6
7
8
GR1
2
3
4
5
6
7
8
T0 (Delay)
1
2
3
4
5
6
7
8
C0 (Filter)
1
OFF DOLBY
Control SURROUND
- P-0
-
P0
-
P0
-
0 0
19.4
0
processing is performed by VC, then it feed-backed to the
delay input after it is added to the doubler described above.
The output of eight taps T1 to T8 is added after performing
reduction processing by GL1~GL8, GR1~GR8, and reduction
processing is performed by the digital attenuator VL or VR,
and an analog output is created by D/A converter after
passing through digital filter, comes out from pin 7 or 8.
The digital attenuated value, delay time and the coefficient
of FIR type low pass filter are set by writing the data on the
register.
This process is performed by loading three data from sub
microcomputer to microcomputer interface.
This unit has four modes as surround mode. The setting
values are described in Table 15-1.
Table 15-1 DSP control factor
THEATER STADIUM NIGHT CLUB CONCERT
P0 P0
P0~ - P0~ -
P0 P0
- M-6
P-4 M-2
M-6 -
P-12
P-12
-
P0
P-18
-
P-2
M-2
P-8
P-10
0 100.0
12.9 93.6
38.7 100.0
71.0 100.0
87.1 0
29.0
45.2
83.9
100.0
0 0.71875
0.28125
114
HALL HALL
P0 P0
P0~ -- P0~ --
P0 P0
M-10 M-8
M-2 P-2
P-4 P-10
P-6 P-16
M-10 -
-
P-6 P-4
M-6 P-8
M-10 P-8
P-12 P-14
19.4 51.6
12.9 71.0
19.4 83.9
22.6 100.0
29.0 0
6.5 64.5
9.7 80.7
25.3 90.4
35.5 100.0
0.59375 0.875
0.40625 0.125
UNIT
dB
msec
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