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9.3.9 Vertical Scaling Control
9.3.10 Horizontal Scaling Control
10 Scaler Configuration
10.1 Overview
TVP5154
4-CHANNEL LOW-POWER PAL/NTSC/SECAM VIDEO DECODER
WITH INDEPENDENT SCALERS AND FAST LOCK
SLES163A – MARCH 2006 – REVISED JULY 2006
Address 3ACh
Default 2100h
7 6 5 4 3 2 1 0
VERT_COEF[7:0]
15 14 13 12 11 10 9 8
Reserved 1 Enable Reserved VERT_COEF[8]
Enabled: Enable vertical and horizontal scaler
0 = Disable scaler (default)
1 = Enable scaler
VERT_COEF [8:0]: Vertical scaling coefficient
VERT_COEF = (Vdesired/Vactive) × 256
Address 3ADh
Default 400h
7 6 5 4 3 2 1 0
HORZ_COEF[7:0]
15 14 13 12 11 10 9 8
Reserved HORZ_COEF[14:8]
HORZ_COEF[14:0]: Horizontal scaling coefficient, MSB five bits are integer values and LSB ten bits are fraction numbers.
HORZ_COEF = Hactive/Hdesired
The TVP5154 contains four independent scalers, one for each video decoder channel. Each scaler is able
to filter and scale both horizontally and vertically to different ratios.
Horizontally, a 7-tap poly-phase filter is used to ensure optimal scaling performance, and can be
configured to scale to any output size below the input resolution, in decrements of two pixels. Vertically a
running average filter is used to filter vertically and can be configured to scale to any output size below the
input resolution.
When scaling horizontally, the output pixels are packed together to allow continuous reading of the pixels.
AVID should be configured so that it qualifies the active pixels, allowing the receiving back end to ignore
nonactive pixels. When scaling vertically, inactive lines are not removed from the output since there is no
internal frame memory. The receiving back end must use AVID to qualify active lines/pixels. AVID can be
configured to be either active or inactive during invalid output lines.
Due to the fact that vertical scaling is performed on a field basis, it is possible that the vertical resolution
will be reduced due to filtering across lines within the field, rather than adjacent lines in the frame. Aliasing
will not occur, but the output image will appear soft vertically. If the desired scaling ration is 0.5, this can
be achieved by simply ignoring every other field. This maintains sharpness, but may introduce aliasing
artifacts.
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