Philips EM5E AA Service Manual page 113

• Digital to Analogue conversion uses three identical 10-bit
DACs.
In the PICNIC there are three nine bits ADCs present for Y, U,
and V. For digitising the Y (luminance), nine bits are used (to
realise a more detailed picture). These nine bits are only
internally used. Via dithering, the nine bits are reduced to eight
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 nine bits for processing.
U/V (colour difference signals) is also sampled with nine bits.
These two nine bit data streams are multiplexed to four bits
data streams. As the perception for colours by the human eye
is less sensitive as for luminance, this reduction is allowed.
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. In addition, 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.
7709
BUS A BUS BUS B
Y DEC
U DEC
V DEC
HA
VA
2
I C
100Hz CONFIGURATION
7709
BUS A BUS BUS B
Y DEC
U DEC
V DEC
HA
VA
2
I C
NATURAL MOTION
Figure 9-11 100 Hz conversion
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:
• 100 Hz (to eliminate field flicker). Only one memory IC
(7714) is used to store one frame. It displays an AABB
sequence.
• Digital Scan (to additional eliminate line flicker). Together
with two memory ICs (7714 and 7740), it displays an
AA'BB' or ABAB sequence.
• Natural Motion (to additional eliminate movement
juddering). Together with two memory ICs (7714 and
7740), it displays an AB'A'B sequence.
Further features of the PICNIC:
• 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).
Circuit Descriptions and Abbreviation List
7714
M
E
M
1
BUS C BUS BUS D
Y FEAT
U FEAT
V FEAT
HD100
VD100
PICNIC/SAA4978H
7726
7714
7740
F
M
M
A
E
E
L
M A B
M
C
1
2
O
N
F C
I
C
BUS C BUS BUS D
Y FEAT
U FEAT
V FEAT
HD100
VD100
PICNIC/SAA4978H
CL 16532044_015.eps
090501
EM5E
• 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.
• 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.
• 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.
• 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.
9.7.4 Eagle (Diagram B3c)
Introduction
Some strong picture improvements are carried out inside the
Eagle, which all contribute to the excellent picture quality.
These improvements are:
• LTI (both horizontal and vertical).
• CTI (only horizontal).
• Peaking (both horizontal and vertical).
• More pixels per line.
• More lines per frame.
• Better colour transitions.
By means of over sampling, the video signals get a sample
frequency of 64 MHz, a bandwidth of 20 MHz, and 1680 pixels
per line (was 32 MHz, 10 MHz and 840 pixels/line). This
requires two extra field memories (MEM4 and MEM5).
The Eagle can handle four different modes:
• Digital Natural Motion (PAL): 100 Hz, 2fH, 2:1 Interlace
(1680 pixels x 625 lines)
• Pixel Plus (PAL): 75 Hz, 2fH, 2:1 Interlace (1680 pixels x
833 lines)
• Double Lines (PAL): 50 Hz, 2fH, 2:1 Interlace (1680 pixels
x 1250 lines)
• Pixel Plus (NTSC): 60 Hz, 2fH, 2:1 Interlace (1680 pixels x
1050 lines)
LTI (Luminance Transient Improvement)
The main objective of LTI is a steeper slope at contrast
transitions (e.g. from 10 mV to 900 mV within 3 pixels i.s.o. 5
pixels for one detail). It is based on waveform altering around a
signal jump.
Important: The LTI, as used in the Eagle, is designed for
interpolated picture contents. This means that for pixel/line
doubling, one of the two pixels/lines is an interpolated value.
When a picture jump is interpolated, you will get extra room to
make it steeper (you get extra pixels to describe the slope).
Without interpolation, you cannot use this kind of LTI.
• LTI can add 'ears' to the waveform at the jump (a kind of
controlled overshoot).
• LTI 'estimates' the frequency of the jump and will adapt the
amplification to this frequency.
• LTI is applied both horizontal as vertical.
9. EN 113