AK8855 Datasheet, PDF (22/81 Pages) Asahi Kasei Microsystems – NTSC/PAL Digital Video Decoder

[ASAHI KASEI]
UV Filter characteristic is as follows.
UV Filter
AK8855
Picture Quality Adjust Process Function
Those Picture Quality Adjust processing such as Contrast adjust function, Brightness adjust function,
Color Saturation adjust function and Color Hue adjust function are integrated in the AK8855.
(1) Contrast Adjust Function
Contrast Adjustment is processed by multiplying Luminance signal ( Y ), by the gain value which is set by
Contrast Control Register ( R/W ) [ Sub Address 0x06 ].
CNTSEL-bit = 0
YOUT = CONT* ( YIN – 128 ) + 125 ;
YOUT
YIN
CONT
: Contrast arithmetic operation result
: before Contrast arithmetic operation
: Contrast coefficient ( register set value )
It is also possible to define the equation as follows by register setting
CNTSEL-bit = 1
YOUT = CONT* ( YIN – 128 ) + 16 ;
YOUT : Contrast arithmetic operation result
YIN : before Contrast arithmetic operation
CONT : Contrast coefficient ( register set value )
Setting is made by [ CNTSEL ]-bit of Control Register ( R/W ) [ Sub Address 0x04 ].
Variable range of Contrast Gain coefficient is from 0 to 1.99 ( 1 / 128 step ) and when the arithmetic operation
result exceeds the above range, it is clipped to the upper-limit of [ 254 ], or the lower-limit of [ 1 ] ( output result
ranges from 16 to 235 when 601 Limit-bit is at [ 1 ] ).
Bit allocation of Contrast Control Register is as follows.
Sub Address 0x06
bit 7
bit 6
bit 5
bit 4
bit 3
CONT7
CONT6
CONT5
CONT4
CONT3
Default Value
1
0
0
0
0
bit 2
CONT2
0
Default Value: 0x80
bit 1
bit 0
CONT1
CONT0
0
0
Sub Address 0x04
bit 7
bit 6
CNTSEL
DTFIX
0
0
bit 5
ODEV
0
bit 4
bit 3
FRMRT1 FRMRT0
Default Value
0
0
bit 2
COLKIL
0
Default Value: 0x00
bit 1
bit 0
ACC
AGC
0
0
MS0319-E-03
22
2004 / 11