VDP313XY datasheet(15/76 Pages) MICRONAS

15 / 76 page

ADVANCE INFORMATION

VDP 313xY

Micronas

2.10.Display Part

In the display part the conversion from digital YCRCB

to analog RGB is carried out (see Fig. 2–17 on

page 20). In the luminance processing path, contrast

and brightness adjustments and a variety of features,

such as black level expansion, dynamic peaking and

soft limiting, are provided. In the chrominance path, the

CRCB signals are converted to 4:4:4 format and filtered

by a color transient improvement circuit. The YCRCB

signals are converted by a programmable matrix to

RGB color space.

The display processor can switch between two sepa-

rate control settings (main/side) for contrast,brightness

and matrix coefficients.

2.10.1.Luminance Contrast Adjustment

The contrast of the luminance signal can be adjusted

by multiplication with a 6-bit contrast value. The con-

trast value corresponds to a gain factor from 0 to 2,

where the value 32 is equivalent to a gain of 1.

2.10.2.Black Level Expander

The black level expander enhances the contrast of the

picture. Therefore the luminance signal is modified

with an adjustable, non-linear function. Dark areas of

the picture are changed to black, while bright areas

remain unchanged. The advantage of this black level

expander is that the black expansion is performed only

if it will be most noticeable to the viewer.

The black level expander works adaptively. Depending

on the measured amplitudes Lmin and Lmax of the low-

pass-filtered luminance (during a programmalbe verti-

cal window) and an adjustable coefficient BTLT, a tilt

point Lt is established by

Lt = Lmin + BTLT×(Lmax − Lmin).

Above this value there is no expansion, while all lumi-

nance values below this point are expanded according

to:

Lout = Lin + BAM ×(Lin − Lt)

A second threshold, Ltr, can be programmed, above

which there is no expansion. The characteristics of the

black level expander are shown in Fig. 2–10and

Fig. 2–11.

The tilt point Lt is a function of the dynamic range of

the video signal. Thus, the black level expansion is

only performed when the video signal has a large

dynamic range. Otherwise, the expansion to black is

zero. This allows the correction of the characteristics of

the picture tube.

Fig. 2–10: Characteristics of the black level expander

Fig. 2–11: Black-level-expansion

a) luminance input

b) luminance input and output

Lmin

BTLT

BAM

Ltr

Lmax

Ltr

BTHR

Lin

Lout

Lmin

Lmax

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