HD49815TF Datasheet, PDF (15/25 Pages) Hitachi Semiconductor – Digital Camera Signal Processor

HD49815TF
2. Color-signal processing block
From
the input
line
memory
block
LINE
SW
C-
limit
+
Pre- RGB
Filter Matrix
+
RGB
Gain
Gamma
correc-
tion
C-G
RGB Setup
WB
YL
Matrix
Axis Base
conver- clipp-
sion ing
To
the zoom
function
Axis
conver-
sion
(WB)
To the luminance
To the AWB
signal processing block detection block
Figure 4 Color-Signal Processing Block
a. C-limit (complementary color clipping level) function
High clipping processing is performed on the complementary color signals independently. High
clipping is set in State Data SP_A2 [0 to 3].
The complementary color signal indicates Gb: (G + Cy), Wr: (Ye + Mg), Wb: (Mg + Cy), and Gr:
(G + Ye).
b. RGB-matrix block
The three primary colors (red, green, and blue) are acquired in the RGB matrix by multiplying
arbitrary coefficients by the four complementary colors (Gb, Wr, Wb, and Gr) and taking the total of
those results. The RGB matrix is designed to support the minimum color moire and to enable free
color reproduction. Arbitrary coefficients are set in State Data SP_A2 [4 to 15]. The following
shows the formula.
Gb
R KRa KRb KRc KRd
B = KBa KBb KBc KBd
Wr
G
KGa KGb KGc KGd
Wb
Gr
State Data SP_A2 [4 to 15]
c. RGB-setup block
The black level of the color signals is variable according to the coefficients of the RGB matrix. The
value calculated by the formula below is subtracted from the color signal to correct the black level.
The subtracted value can be set externally and is set in State Data SP_A3 [0 to 2].
Formula = −[48 × Σ (Matrix data) × 2³]
d. RGB-gain block
The RGB gain value acquired in the AWB control is set in the RGB gain circuit to improve the
white reproduction performance. As it is set prior to the gamma correction, it changes the gamma
correction amount. The RGB gain can be set in State Data SP_A3 [3 to 5] from 1 to 256 times.
(The G gain is set from 1 to 128 times.)
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