6.5.3 YUV(4:4:4) to RGB(888) conversion
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)
6.6 YUV Adjustment
The YUV adjustment unit provides two different modes, selected by
VInADJUSTLEVEL.ADLMODE:
•
VInADJUSTLEVEL.ADJMODE = 0: YUV amplification mode
•
VInADJUSTLEVEL.ADJMODE = 1: YUV replacement mode
Brightness and
contrast
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
out
is calculated as follows:
•
Y
out
= (Y
in
– 128) • AY[4:0] / 16 + OY[7:0]
Y
out
is clamped to its maximum (235) and minimum (16) value.
Amplification mode
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
out
and V
out
are calculated as
follows:
•
U
out
= (U
in
– 128) • AU[4:0] / 16 + 128
•
V
out
= (V
in
– 128) • AV[4:0] / 16 + 128
U
out
and V
out
are clamped to their maximum (235) and minimum (16) values.
Replacement mode
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
out
= AUREP[7:0]
•
V
out
= AVREP[7:0]
Coefficient format
The 5-bit coefficients AY[4:0], AU[4:0], AV[4:0] are used in fixed point notation, i.e.
10000
B
corresponds to 1.
Therefore the size of each of the 32 steps calculates to 2
-4
= 0.0625 and the
coefficients range from 00000
B
= 0 to 11111
B
= 1.9375.
Chapter 6
Video Input (Ravin-M only)
166
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