Philips EM3E, Руководство по обслуживанию, Страница: 49 / 120

Circuit Descriptions and Abbreviation List GB 101 EM3E 9.
more detailed picture). These 9 bits are only internally used.
Via dithering the 9 bits are reduced to 8 bits and this data is
stored into memory. The data in the memory is fed back to
the PICNIC and via un-dithering the data is again reproduced
to 9 bits for processing.
U/V (colour difference signals) is also sampled with 9 bits.
These two 9 bit data streams are multiplexed to 4 bits data
streams. As the perception for colours by the human eye is
less sensitive as for luminance, this reduction is allowed.
9.7.3 100 Hz Conversion
The main task of the PICNIC is the conversion from 50Hz to
100Hz for YUV and HV-sync. In order to remove 'large area
flicker' (especially visible in a white picture), the field-rate of
the video is doubled by the FBX6. A 50/60 Hz frame
frequency is converted to 100/120 Hz. Also the line
frequency (16 kHz) is doubled (32 kHz).
Basically, when the video input contains fields A, B etc..., the
conversion provides an AABB sequence on the display. The
actual conversion is done in the first Field Memory (by
reading it twice at double speed, while writing it once.
Figure 9-8
For extra 100 Hz features, it is possible to add an extra IC to
the PICNIC. This IC, called the ‘Field And Line CONverter IC’
(FALCONIC), has three modes:
1.
100 Hz (to eliminate field flicker). Only one memory IC
(7714) is used to store one frame. It displays an AABB
sequence.
2. Digital Scan (to additional eliminate line flicker).
Together with two memory ICs (7714 and 7740), it
displays an AA’BB’ or ABAB sequence.
3. Natural Motion (to additional eliminate movement
juddering).
Together with two memory ICs (7714 and 7740), it
displays an AB’A’B sequence.
9.7.4 Dual Screen Compression
The PICNIC can provide horizontal video compression up to
50 %. The compress mode can be used to display dual
screens with Teletext (only for wide-screen sets).
9.7.5 The Panorama Mode
To fit 4:3 pictures into a 16:9 display, it is possible to apply a
panoramic horizontal distortion, to make a screen-fitting
picture without black sidebars or lost video.
The centre horizontal gain is programmable and the side gain
is automatically adapted to make a screen-fit.
9.7.6 Automatic Aspect Ratio Adaptation (AARA)
This feature uses data from the 'black bar detection circuit' to
adapt the vertical and horizontal amplitude to an aspect ratio
belonging to the display, without the black bars.
9.7.7 Colour Transient Improvement (CTI)
At CVBS video signals, the bandwidth of colour signals is
limited to 1/4 of the luminance bandwidth. Transients
between areas of different colours are therefore not very
sharp.
The PICNIC can steepen these transients artificially with a
time manipulation algorithm.
9.7.8 Dynamic Contrast
To make the contrast (black/white) range wider, Philips has
invented Dynamic Contrast. It uses the digital memory used
in 100 Hz sets. It measures every A-field (25 x per second),
and digitally analyses where on the greyscale most of the
image is located.
If it is a relatively dark image, the lighter part of that image is
stretched towards white, so that more contrast will become
visible in that picture.
If it is a relatively light image, the darker part of that image is
stretched towards black, so that these darker parts will have
more contrast.
When the image is in the middle of the greyscale, both dark
and light parts are stretched.
9.8 Video: High-end Output Processor (HOP) and
TOPIC (diagram B4)
9.8.1 General
The YUV-signals from the PICNIC are fed to the HOP (High-
end Output Processor, TDA9330). The video and geometry
control parts are integrated in the HOP. Also the RGB-signals
for TXT/OSD (from the
m
P), are inserted via the HOP. The
geometry part delivers the H-drive, EW-drive, V-drive and
also a drive signal for rotation.
The main functions of the HOP are:
•
Video control (contrast, brightness, saturation, etc.).
• Deflection drive.
• 2nd RGB interface for OSD/TXT.
• Peak White Limiting.
• Cut-off control and White Drive (RGB outputs).
• Geometry control.
The TOPIC (The most Outstanding Picture improvement IC,
item 7302, type TDA9178), is an optional IC between the
PICNIC and the HOP. It has the following (picture
improvement) functions:
•
Luminance Transient Processor (LTP), for detail
enhancement.
• Chrominance delay circuitry, to compensate timing
differences between Y and C.
• Spectral processor , for improved sharpness and colour
transient improvement (CTI).
• Colour vector processor, for skintone correction, green
enhancement and blue stretch.
• Measure and detection circuitry, for AutoTV.
CL 16532044_015.eps
090501
BUS A BUS
PICNIC/SAA4978H
NATURAL MOTION
B BUS BUS C BUS BUS D
M
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1
M
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2
F
A
L
C
O
N
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Y FEAT Y DEC
U FEAT U DEC
V FEAT V DEC
HD100 HA
VD100 VA
BUS A BUS
PICNIC/SAA4978H
100Hz CONFIGURATION
B BUS BUS C BUS BUS D
M
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I C
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Y FEAT Y DEC
U FEAT U DEC
V FEAT V DEC
HD100 HA
VD100 VA
7709
7714
7714
7709
7740
7726
A B
F C
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