Panasonic EURO 4 Chassis, Technical Manual

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3DQDVRQLF
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Chapter 3 EURO 4H Supplement
2.3.2. Horizontal Scaler
The horizontal scaler which is fed the 4:2:2 YC
r
C
b
signal from the previously discussed stage is used to
convert the YCrCb signals from 20.25MHz to a Line
Locked output Clock (LLC) of 13.5MHz, under the
control of the internal fast processor.
This conversion of the output clock frequency to
13.5MHz allows the support of the 100Hz system.
This up-conversion taking place in IC1503 discussed
in chapter 3 section 2.5.
After the above conversion process has taken place
the YCrCb signals are then fed to the following Black
Line Detector stage.
2.3.3. Black-Line Detector
When a letterbox format signal is processed black
areas at the top and bottom of the picture are visible.
To over come this the picture is either zoomed or
shifted.
The VPC3215 IC1501 supports this feature using a
letterbox detector. The detector is used to detect
black video lines by measuring the signal amplitude
during active video. For every field the number of
black lines are measured, compared to the previous
measurement and the result is stored in the I
2
C
register BLKLIN. To adjust the picture amplitude the
external controller reads this register, calculates the
vertical
scaling co-efficients (vertical sawtooth
parameters, horizontal scaling etc.) and transfers the
new settings to the VPC IC1501.
The letterbox signals containing logos on the left and
right side of the black areas are processed as black
lines, while subtitles inserted in the black areas are
processed as non-black lines. Therefore the subtitles
are visible on the screen. Dark video scenes with a low
contrast level compared to the letterbox area are
indicated by a BLKPIC bit.
Skew
Filter
Horizontal
Scaler
BlackLine
Detector
Luma
Chroma
From
Colour Decoder
To
Display
Processor
Luma
Chroma
Scaler Stage