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6. SMALL SIGNAL PANEL
MG5.1E
6.8 The TOPIC (The most Outstanding Picture improvement IC)
Figure 6-14
CL 86532047_024.eps
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PAL-SIGNAL FIELD A
VIDEO INPUT
SANDCASTLE INPUT
V-PULSE INTERNAL
NOISE DETECTOR MEASURE
The different items are explained now:
1. Luminance transient processor
•
The luminance is measured within a window (internal
controlled). Depending on the luminance contents,
improvements are done to get the most details. This is
called analogue histogram processing. The window can
be controlled via I2C.
•
Also black stretch is built-in to improve the contrast of
the luminance signal. For this the lowest level of the
signal is detected in the TOPIC. In the same window (as
above) the black level is detected. If this black level
differs from the blackclamping level, then the difference
is partly compensated (black level offset).
•
Another improvement for luminance is the gamma
correction, but this is depending on the black level
offset.
2. Chrominance delay This is necessary to compensate
timing differences between luminance and chrominance.
3. Spectral processor
•
The sharpness can be improved: Emphasise big black/
white transients with a “steepness control” and
emphasise on details with “peaking control”.
•
CTI improves the colour transients.
•
For saturated red and magenta the luminance
sharpness is increased (colour dependent sharpness).
4. Colour vector processor
•
Skintone correction: This is special for NTSC to mask
transmission/HUE-control.
•
Green enhancement: Green with low saturation is more
amplified.
•
Blue stretch: Colours close to white are changed a little
to blue, to get a brighter impression.
5. Measurement and detection (fig 6-14)
•
The noise detector measures the noise in the frame
flyback during one video line without videosignal
(=black). The TOPIC takes the average of 20 frames.
This average value can be read via I2C. The noise
measurements is switched off when the videosignal
comes from a VCR. These signals are not reliable.
•
The TOPIC has three A/D converters. Only two of them
are used.
–
On pin 3 of IC7402 a voltage comes in from the light
sensor. This voltage depends on the daylight-
luminance. During daytime a higher contrast-level is
needed than in the evening when it becomes dark.
This is most convient for the customer.
–
On pin 5 of IC7402 the beam current information
(derived from EHT-info) is coming-in. Dependent of
the beam current, YUV-levels can be adapted.
•
Also the number of high frequencies are measured and
there is a detection when the picture contents changes
very rapid. All this information together is used for auto-
TV.
6. The TOPIC uses internal a window where the luminance
pattern and blacklevel is measured. This window is defined
such that subtitles, logos or black bars (for letter box) have
no influence on the results measured. Results in the middle
of the window have more influence on the postprocessing.
On pin 1 of the TOPIC the sandcastle from the HOP is fed
which is used as reference for timing. The clamping/blanking
and vertical retrace are used.
