AK8857VQ Datasheet, PDF (64/105 Pages) Asahi Kasei Microsystems – Dual Channel Digital Video Decoder

[AK8857VQ]
Image quality adjustments
Image quality adjustments consist of contrast, brightness, sharpness, color saturation, and hue
adjustment. All image quality adjustments are disabled during the vertical blanking interval, but
contrast and brightness adjustment can be enabled by the register setting.
1. Contrast adjustment
CONT[7:0]-bits: For contrast adjustment; default value 0x80 (no adjustment)
Contrast adjustment involves multiplication by the gain factor setting in this register. The
equation of the multiplication can be modified by register setting as follows.
If CONTSEL = [0], then YOUT = (CONT/128) x (YIN – 128) + 128
If CONTSEL = [1], then YOUT = (CONT/128) x YIN
YOUT: Contrast obtained by the calculation
YIN: Contrast before the calculation
CONT: Contrast gain factor (register setting value)
The gain factor can be set in the range 0~255. If the calculated value is outside the specified
contrast range, it is clipped to the upper ‘254’ or lower ‘1’ limit. With a control bit 601LIMIT setting
of [1], the output will be in the range 16~235.
○CONTSEL-bit : Settings for contrast adjustment Inclination
CONTSEL -bit
Inclination
[0]
Toward luminance of 128
[1]
Toward luminance of 0
Notes
2. Brightness adjustment
BR[7:0]-bits: For brightness adjustment; settings in 2’s complement;
default value 0x00 (no adjustment)
Brightness adjustment involves multiplication of the 8Bit data luminance signal, after ITU-R BT.601
conversion, by the gain factor setting in this register, as follows.
YOUT = YIN + BR
YOUT: Brightness obtained by the calculation
YIN: Brightness before the calculation
BR: Brightness gain factor (register setting value)
The gain factor can be set in the range -127 to +127 in steps of 1, by 2’s complement entry. If the
calculated value is outside the specified contrast range, it is clipped to the upper ‘254’ or lower ‘1’
limit. With a control bit 601LIMIT setting of [1], the output will be in the range 16~235.
3. Color saturation adjustment
SAT[7:0]-bits: For color saturation adjustment; default value 0x80 (no adjustment)
Saturation adjustment involves multiplication of the color signal by the gain factor setting in
this register. The calculated result is U/V demodulated.
The gain factor can be set in the range 0 to 255/128, in steps of 1/128.
MS1189-E-01
-64-
2010/12