MB87P2020 Datasheet, PDF (171/356 Pages) Fujitsu Component Limited. – Colour LCD/CRT/TV Controller

Graphic Processing Unit
3.7 YUV to RGB conversion
Full support for YUV to RGB conversion as described in this section is only available for MB87P2020-A
(Jasmine).
MB87J2120 (Lavender) is able to handle YUV444 and YUV422 in a limited manner. It simply ignores the
color components of the color value and displays it in 256 step grayscale format also called ’achromatic
mapping’.
This behaviour is also available for Jasmine as alternative mapping for YUV422, YUV444, YUV555 and
YUV655.
3.7.1 YUV422 Demultiplexing and Chrominance Interpolation
The YUV422 format is special in the respect that it implies chroma sub-sampling and distribution of U(Cb)
and V(Cr) values on every other pixel (see figure 3-4 below).
Luminance … _{Y 2i – 2 Y 2i – 1}
Y _2i
Y _{2i + 1} Y _{2i + 2} Y _{2i + 3} ^{… 8 bits each}
Chrominance … _{U2i – 2 V 2i – 2}
U_2i
V _2i
U_{2i + 2} V _{2i + 2} ^{… 8 bits each}
Chroma_{2i – 2}
Chroma_2i
Chroma_{2i + 2}
Figure 3-4: Memory map for pixels in YUV422 format. Pixels on even positions carry U-chrominance,
those on odd positions V-chrominance, i = 0, 1, 2, …
Therefore, pairs of pixels have to be fetched from memory to obtain complete color information. This re-
sults in the constraints that layer’s horizontal first pixels (FX) as well as their horizontal window size (WX)
must not be odd. Due to internal processing of pixels in portions of display segments the horizontal display
offset (OX) is also limited to even positions. These restrictions are enforced automatically by GPU by ig-
noring the LSBs of the parameters mentioned before.
In order to process the YUV422 format in the matrix (see next section) the PixelPump within the DFU does
the necessary demultiplexing to assign each pixel the complete chrominance information, i.e. pixels arriv-
ing at the matrix have the structure shown in figure 3-5.
Luminance … _{Y 2i – 2 Y 2i – 1}
Y _2i
Y _{2i + 1} Y _{2i + 2} Y _{2i + 3} ^{… 8 bits each}
Chrominance …
U_{2i – 2}
U_2i
U_{2i + 2}
… 8 bits each
…
V_{2i – 2}
V _2i
V_{2i + 2}
… 8 bits each
Figure 3-5: Pixel structure after YUV422 demultiplexing. Although now each pixel is assigned complete
chrominance information there is still a chrominance sub sampling
The effect of chrominance sub sampling can be decreased and hence the appearance of the image improved
by applying a linear interpolation between consecutive chrominance values as illustrated in figure 3-6. This
interpolation is controlled by a configuration register.
GPU Control Information
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