VDP3108B datasheet(13/72 Pages) MICRONAS

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PRELIMINARY DATA SHEET

VDP 31xxB

Micronas

2.4. Horizontal Scaler

The 4:2:2 YCrCb signal from the color decoder is pro-

cessed by the horizontal scaler. The scaler block allows

a linear or nonlinear horizontal scaling of the input video

signal in the range of 0.25 to 4. Nonlinear scaling, also

called “panorama vision”, provides a geometrical distor-

tion of the input picture. It is used to fit a picture with 4:3

format on a 16:9 screen by stretching the picture geome-

try at the borders. Also, the inverse effect can be pro-

duced by the scaler. A summary of scaler modes is given

in Table 2–2.

The scaler contains a programmable decimation filter, a

1-line FIFO memory, and a programmable interpolation

filter. The scaler input filter is also used for pixel skew

correction, see 2.3.9. The decimator/interpolator struc-

ture allows optimal use of the FIFO memory. The con-

trolling of the scaler is done by the internal Fast Proces-

sor.

Table 2–2: Scaler modes

Mode

Scale

Factor

Description

Compression

4:3

→ 16:9

0.75

linear

4:3 source displayed on a

16:9 tube,

with side panels

Panorama

4:3

→ 16:9

non-

linear

compr

4:3 source displayed on a

16:9 tube,

Borders distorted

Zoom

4:3

→ 4:3

1.33

linear

Letterbox source (PAL+)

displayed on a 4:3 tube,

vertical

overscan

with

cropping of side panels

Panorama

4:3

→ 4:3

non-

linear

zoom

Letterbox source (PAL+)

displayed on a 4:3 tube,

vertical overscan, bor-

ders distorted, no crop-

ping

2.5. Black-Line Detector

In case of a letterbox format input video, e.g. Cinema-

scope, PAL+ etc., black areas at the upper and lower

part of the picture are visible. It is suitable to remove or

reduce these areas by a vertical zoom and/or shift op-

eration.

The VDP 31xxB supports this feature by a letterbox de-

tector. The circuitry detects black video lines by measur-

ing the signal amplitude during active video. For every

field the number of black lines at the upper and lower

part of the picture are measured, compared to the pre-

vious measurement and the minima are stored in the

I2C-register BLKLIN. To adjust the picture amplitude, the

external controller reads this register, calculates the ver-

tical scaling coefficient and transfers the new settings,

e.g. vertical sawtooth parameters, horizontal scaling co-

efficient etc., to the VDP.

Letterbox signals containing logos on the left or right

side of the black areas are processed as black lines,

while subtitles, inserted in the black areas, are pro-

cessed as non-black lines. Therefore the subtitles are

visible on the screen. To suppress the subtitles, the verti-

cal zoom coefficient is calculated by selecting the larger

number of black lines only. Dark video scenes with a low

contrast level compared to the letterbox area are indi-

cated by the BLKPIC bit.

2.6. Test Pattern Generator

The YCrCb outputs of the front-end can be switched to

a test mode where YCrCb data are generated digitally

in the VDP 31xxB. Test patterns include luma/chroma

ramps, flat fields and a pseudo color bar pattern.

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