MB87P2020 Datasheet, PDF (157/356 Pages) Fujitsu Component Limited. – Colour LCD/CRT/TV Controller

Graphic Processing Unit
2.3 Mapping from Logical to Intermediate Color Space
Table 2-1 lists the available mappings from logical to intermediate color space. The term direct designates
an immediate mapping wire by wire with more significant bits being clamped to zero as needed. For in-
stance, logical 2bpp is mapped directly onto intermediate RGB111 this way: I[3:0] = “0” & L[1:0].
The term lookup means using the look-up table for mapping. The term aligned designates a mapping in
which wires are connected in groups according to color channels with appropriate value scaling. For in-
stance:
• logical RGB555 to intermediate RGB666 (i.e. expansion of color channel bit with):
I[17:0] = L[14:10] & L[14] & L[9:5] & L[9] & L[4:0] & L[4]
• logical RGB555 to intermediate RGB333 (i.e. reduction of color channel bit with):
I[8:0] = L[14:12] & L[9:7] & L[4:2]
The term matrix designates application of a matrix multiplication. When transforming logical YUV422 to
an RGB intermediate format an optional chrominance interpolation may be applied (see 3.7). The term ach-
romatic describes a mapping from YUV to RGB color spaces by dropping chrominance information and
transforming the luminance to gray levels. All matrix and achromatic mappings are auto aligned to their
target bit with¹.
The mapping from logical to intermediate color space is controlled by the settings for logical color space in
the layer’s respective layer description record and the setting of intermediate color space, matrix parame-
ters, and transfer bit in the merging description record.
2.4 Mapping from Intermediate to Physical Color Space
Table 2-2 lists the mappings from intermediate to physical color space. The terms direct and aligned keep
their meaning. The term modulated designates the usage of the Duty Ratio Modulator (see 3.8). The purpose
of this unit is to provide additional (pseudo-) levels (shades of hue or gray) for output, i.e. virtually expand
the color resolution in the physical color space. This is achieved by tuning the duty ratio of actually existing
physical bits. Accordingly, the term gamma means employing the gamma tables for mapping.
The mapping is controlled by the settings of intermediate color space in the merging description record and
the setting of physical color space in the display interface record.The resulting mapping from logical to
physical color spaces is shown by table 2-3. It is contains the possible path of transformation from pixel in
VideoRAM to those on the physical display.
1. Since matrix results are always in RGB888 color space this auto aligning implies at most a reduction of bit-
width whereas achromatic mapping can result in both, bit width reduction as well as expansion (see also
3.7.2).
Color Space Concept
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