Panasonic EURO 4 Chassis Technical Manual page 47

17.6. Scaler Stage
The luma and chroma signals output from the colour
decoder are fed to the following scaler stage and the
Skew filter.
17.6.1.Skew Filter
The skew filter is used to ensure that the signal
being processed is at the same timing as the system
clock.
As there is no way for the VDP
whether the signal that it is processing is a standard
signal or a non-standard signal, e.g. VCR input, the
system clock is free running.
The skew filter which is controlled by the internal
Horizontal Phase Lock Loop1 (PLL1), (located in the
sync and deflection block discussed later), produces
a phase shift which ensures that the system clock
and source signal are at the same timing.
The luma and chroma signals are then fed to the
Horizontal scaler.
17.6.2.Horizontal Scaler
The 4:2:2 YC C signal is fed to the horizontal scaler.
r b
The horizontal scaler is used to fit a picture with 4:3
format on a 16:9 screen by stretching the picture
geometry at the borders, the inverse effect can also
be produced by the scaler. A summary of the scaler
modes is given below.
Mode Scale Factor
Compression 0.75 linear
4:3 -> 16:9
Panorama non-linear
4:3 -> 16:9 compression
Zoom 4:3 -> 1.33 linear
4:3
Panorama non-linear
4:3 -> 4:3 zoom
Scaler Stage
Luma
From
Colour Decoder
Chroma
IC601 to know
Description
4:3 source displayed on a 16:9
tube, with side panels
4:3 source displayed on a 16:9
tube, Borders distorted
Letterbox source (PAL+)
displayed on a 4:3 tube, vertical
overscan, borders distorted, no
cropping
letterbox source (PAL+)
displayed on a 4:3 tube, vertical
overscan, borders distorted, no
cropping
Skew
Filter
The scaler
decimation filter, a 1-line delay FIFO memory and a
programmable interpolation filter.
The controlling of the scaler being performed by the
internal Fast Processor.
17.6.3.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 VDP3120
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
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 VDP IC601.
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.
BlackLine
Detector
Horizontal
Scaler
47
itself contains a
IC601 supports this feature using a
Luma
To
Display
Processor
Chroma
3DQDVRQLF
programmable
2
C