Yuv(4:4:4) To Rgb(888) Conversion; Yuv Adjustment - NEC µPD72257 Preliminary User's Manual

Chapter 6

6.5.3 YUV(4:4:4) to RGB(888) conversion

6.6 YUV Adjustment

Brightness and
contrast
Amplification mode
Replacement mode
Coefficient format
166
The YUV(4:4:4) to RGB(888) conversion is done with following formulas:
• R = 1.164 • (Y-16) + 1.596 • (V-128)
• G = 1.164 • (Y-16) – 0.813 • (V-128) – 0.391 • (U-128)
• B = 1.164 • (Y-16) + 2.018 • (U-128)
The YUV adjustment unit provides two different modes, selected by
VInADJUSTLEVEL.ADLMODE:
• VInADJUSTLEVEL.ADJMODE = 0: YUV amplification mode
• VInADJUSTLEVEL.ADJMODE = 1: YUV replacement mode
In both modes the brightness and contrast can be enhanced by adjusting the Y
channel of the YUV(4:4:4) encoded data. This is achieved by applying an offset
and amplifying the value.
The offset is set by VInADJUSTLEVEL.OY[7:0] value, the amplification factor is
set by VInADJUSTLEVEL.AY[4:0].
The output Y is calculated as follows:
out
• Y = (Y – 128) • AY[4:0] / 16 + OY[7:0]
out in
Y is clamped to its maximum (235) and minimum (16) value.
out
In amplification mode (VInADJUSTLEVEL.ADJMODE = 0) the colour saturation
can be changed by amplifying the U and V values.
The amplification factors are set by VInADJUSTLEVEL.AU[4:0] and
VInADJUSTLEVEL.AV[4:0]. The output values U
follows:
• U = (U – 128) • AU[4:0] / 16 + 128
out in
• V = (V – 128) • AV[4:0] / 16 + 128
out in
U and V are clamped to their maximum (235) and minimum (16) values.
out out
The replacement mode (VInADJUSTLEVEL.ADJMODE = 1) performs a
recolouring of monochrome images by replacing the original U and V values by
VInADJUSTLEVEL.AUREP[7:0] respectively VInADJUSTLEVEL.REP[7:0]:
• U = AUREP[7:0]
out
• V = AVREP[7:0]
out
The 5-bit coefficients AY[4:0], AU[4:0], AV[4:0] are used in fixed point notation, i.e.
10000 corresponds to 1.
B
Therefore the size of each of the 32 steps calculates to 2
coefficients range from 00000
Preliminary User's Manual S19203EE1V3UM00
Video Input (Ravin-M only)
and V
out
= 0 to 11111 = 1.9375.
B B
are calculated as
out
-4
= 0.0625 and the