PRELIMINARY DATA SHEET
VDP 31xxB
2.4. Horizontal Scaler
2.5. Black-Line Detector
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
formatona16:9screenbystretchingthepicturegeome-
try at the borders. Also, the inverse effect can be pro-
ducedbythescaler. Asummaryofscalermodesisgiven
in Table 2–2.
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
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.
2
I C-registerBLKLIN. Toadjustthepictureamplitude, 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
visibleonthescreen. Tosuppressthesubtitles, theverti-
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.
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
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.
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
Micronas
13
MICRONAS [ MICRONAS ]
