vpx3224d ETC-unknow, vpx3224d Datasheet - Page 15

• Manufacturer Part Number: vpx3224d
• Description: Video Pixel Decoders
• Manufacturer: ETC-unknow

Micronas
PRELIMINARY DATA SHEET
2.5.1. Horizontal Resizer
The operating range of the horizontal resizer was cho-
sen to serve the widest possible range of applications
and source formats (number of lines, aspect ratio, etc...).
Table 2–2 lists several examples for video sourced from
525/625 line TV systems.
The horizontal resizer alters the sampling raster of the
video signal, thereby varying the number of pixels (NPix)
in the active portion of the video line. The number of pix-
els per line is selectable within a range from 32 to 864
in increments of 2 pixels (see section 2.10.: Windowing
the Video Field). Table 2–2 gives an overview of several
supported video rasters. The visual quality of a sampling
rate conversion operation depends on two factors:
– the frequency response of the individual filters, and
– the number of available filters from which to choose.
The VPX is equipped with a battery of FIR filters to cover
the five octave operating range of the resizer. Fig. 2–12
shows the magnitude response of five example filters
corresponding to 1054, 526, 262, 130, and 32 pixels.
The density of the filter array can be seen in Fig. 2–13.
The magnitude response of 50 filters lying next to each
other are shown. Nevertheless, these are only 10% of all
filters shown. As a whole, the VPX comes with a battery
of 512 FIR filters. Showing these 512 Filters in Fig. 2–12
would result in a large black area. This dense array of fil-
ters is necessary in order to maintain constant visual
quality over the range of allowable picture sizes. The al-
ternative would be to use a small number of filters whose
cutoff frequencies are regularly spaced over the spec-
trum. However, it has been found that using few filters
leads to visually annoying threshold behavior. These ef-
fects occur when the filters are changed in response to
variations in the picture size.
Filter selection is performed automatically by the internal
processor based on the selected resizing factor (NPix).
This automated selection is optimized for best visual
performance.
–10
–12
–10
–20
–30
–40
Fig. 2–12: Freq. response of 5 widely spaced filters
dB
Fig. 2–13: Freq. response of 50 neighbored filters
dB
–2
–4
–6
–8
0
0
0
0
VPX 3225D, VPX 3224D
0.5
10
1
1.5
20
2
30
2.5
MHz
MHz
40
15
3