
On-Screen Display
9-23
where
A value of zero in the Horizontal Filter Scale register (Register 277,
page 4-64
) is equivalent to an increment of 256. The raster mapper
increment value is sampled at the new field boundary to allow the host
to change the scale factor between fields.
means to round the value x to the smallest integer larger than x.
Clearing the Horizontal Filter Enable bit disables the interpolation filter,
leaving the data unfiltered. The filter is automatically disabled during the
auxiliary data area of the display.
9.9 On-Screen Display
The Video Interface integrates a flexible OSD Controller that allows the
overlay of a bitmap image on top of the decoded video or background.
The OSD image may be written to SDRAM by the host (internal mode)
or supplied to the L64105 from an external device (e.g., a character
generator) on the EXT_OSD[3:0] input pins.
The OSD image is not horizontally filtered and is thus always the same
size regardless of the resolution or mode of the video data. In addition,
pan and scan of the video data does not affect the position of the OSD
overlay. The OSD Controller also includes a chroma filter designed to
enhance the edge conditions of OSD areas. This filter can be enabled
by setting the OSD Chroma Filter Enable bit in Register 274 (
page 4-61
).
Table 9.6
Raster Mapper Increment Value by Source Resolution
Target
Source
Ratio
(Source:Target)
Increment
Main
Reads/Line
720
352
0.488
126
44
720
480
0.667
171
60
720
544
0.755
194
68
720
640
0.888
228
80
704
352
0.500
128
44
704
480
0.682
175
60
704
544
0.755
198
68
704
640
0.909
233
80
x