Philips EM5E AA Service Manual page 114

EN 114 9.
• LTI is amplitude dependent. This means that only 'big'
jumps are processed. It works with a threshold, which is
coupled to the noise meter via the Auto TV software.
• LTI is also frequency dependent. This means that it is
distributed over the slopes. When there are many steep
slopes in the signal, LTI will only process the steepest
ones. If there are only a few slopes, LTI will process all of
them. This is fully hardware implemented.
Luminance Y
B
C
Figure 9-12 Horizontal LTI
For horizontal LTI, the number of pixels is doubled (64 MHz) by
means of interpolation. Pixel A at the transition will keep its
luminance value, while the (new) pixels B can have a
luminance value of zero to max. 31. For example:
• Pixels B can keep the same value (gain = 0)
• Pixels B can get the value of C and C' (gain = 8), which will
give a steeper slope.
• Pixels B can also get the value of D and D' (gain = 31),
which will give an even steeper slope with the so-called
'ears'. These 'ears' will give a contrast improvement.
For CTI, the same principle is used, in order to get better
colour transitions.
833
samples
Figure 9-13 Vertical LTI
The principle for vertical LTI is the same as for horizontal LTI.
The shift from 625 to 833 lines is done by means of a scaler.
With these extra interpolated samples, it is possible to create
steeper slopes, possibly with 'ears'.
Peaking/Coring
The objective of 'peaking' is contrast improvement (e.g. from 50
mV to 70 mV for one detail).
PP PP
It uses a noise threshold (coring = non-linear filtering around
zero-level), thus it works everywhere in the picture (except
below the threshold level).
The added difference signal is frequency dependent, which
results in frequency dependent contrast improvement. When
the difference signal becomes too large, the peaking is reduced
(smartness).
EM5E Circuit Descriptions and Abbreviation List
D'
Original slope
Added interpolated
C'
B
A
gain=0
gain=8
D gain=31
spatial X or Y
CL 16532149_083.eps
Original samples
detail
Added interpolated
CL 16532149_084.eps
Amplitude
To obtain above shown filter characteristic, filters are set at
three parameters (see A, B, and C). In this way, only the higher
pixels
frequencies are 'lifted'. After sending the luminance signal
through these filters, the filter output is added to the original
signal. In this way, the so-called 'ears' are created, together
with the steeper slopes. These 'ears' will give a contrast
improvement at details.
Both horizontal and vertical peaking is amplitude dependent:
the higher the signal jump, the lower the peaking. This is done
061201
to avoid that high jumps get big 'ears', because this will
introduce nasty contouring. To avoid peaking on noise levels,
coring is used. The coring threshold is set via the Auto TV
software, by means of the noise meter.
Therefore, the result is that only details are processed by the
peaking.
The horizontal peaking is also frequency dependent: it is
possible to perform peaking around three frequencies (when
combined, it is even possible to peak at variable frequencies).
In Auto TV, this feature is software coupled to the sharpness
meter, in order to get the most optimal filter characteristic.
The vertical peaking works on a fixed frequency.
Colour Enhancements
In the FBX6 (as used in the EM3E), the TOPIC handled the
colour enhancement features, such as: 'skin tone correction',
'blue stretch', and 'green enhancement'. In the new FBX7, all
this is done by the Eagle IC.
samples
Output
The YUV signals presented to the HOP come from the Eagle.
These three signals have all the same circuitry so it is explained
once (for Y).
071201
Y-EAGLE
(pin54)
The YUV signals are first filtered by a 64 MHz passive filter
(L5739 with C's). Because the output signals from the Eagle
are too small to drive the HOP directly, they are amplified by the
circuit around TS7731 and TS7728. The gain is determined by
R3791, R3788, and R3807. For the Y-signal the gain is 2, for
the U-signal it is 1.33, and for the V-signal it is 1.05.
PEAKING
2.3Mc 4Mc 8Mc
Frequency
A B C
Figure 9-14 Peaking
2700
5700
GND
+8V
5739
GND GND GND GND
Figure 9-15 YUV Output Filter
'ear'
'ear'
CL 16532149_085.eps
131201
3700
Y100
GND
7728
7731
GND GND GND
CL 26532041_076.eps
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