
6-8
Video Interface and On-Screen Display
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
Table 6.5 compares the bits required and frame storage necessary for
regular memory mode and reduced memory mode with chroma line
repeat. The information in
Table 6.5 is based on a full PAL eld with 288
lines/eld.
Table 6.5
Memory Mode
Specications
6.4
Horizontal Post-
Processing
Filter
The L64005 integrates an output interpolation lter that can be used to
interpolate pixels on a scan line so that there are up to 720 pixels output
for each line, regardless of the input picture resolution. The lter is also
used to provide ne scale pan and scan to within 1/8 pixel during pan
and scan mode.
6.4.1
Filter
Specication
The interpolation lter is implemented using an eight-tap polyphase lter.
The L64005 can generate up to eight unique sub-pixel values between
two consecutive pixels on a scan line. Exactly which pixels are generated
depends on the ratio between the width of the source image and the
width of the target image (typically 720 pixels).
There are two frequency responses that can be selected under software
control, labeled A and B. Note that Filter A has a slightly higher cut off
frequency. Figures
6.3 through
6.6 shows the characteristics of the inter-
polation lter.
Memory Mode
Frame
Segments
B-frame
Bits
Forward
and
Backward
Anchor
Bits
required
Frames
Stored
Regular
72
4,976,640
9,953,280
14,929,920
3.000
Reduced with
chroma line repeat
40
2,764,800
9,953,280
12,718,080
2.556