AK8851 Datasheet, PDF (31/80 Pages) Asahi Kasei Microsystems – NTSC/PAL/SECAM Digital Video Decoder

ASAHI KASEI
[AK8851]
(7) Luminance Bandwidth Adjustment
To maximize the compression ratios in MPEG and other digital video formats, it is often desirable to limit the Luminance
bandwidth through pre-processing before compression. T.
For this purpose, Luminance signal band-limiting-filters can be selected. When these filters are not used, the frequency
response of the Luminance signal tracks the decimation filter characteristics.
Selection of Luminance band-limiting-filters is done by [LUMFIL1:LUMFIL0]-bit of [Image Control Register](R/W)[ Sub
Address 0x10].
Selectable filter characteristics are shown below.
Frequency [MHz]
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
10
0
-10
-20
-30
-40
-50
-60
Bit allocation of [Image Control Register]-bit is shown below.
Sub Address 0x10
bit 7
bit 6
bit 5
bit 4
bit 3
VBIIMGCTL
SEPIA
LUMFIL1
LUMFIL0 SHCORE1
Default Value
0
0
0
0
0
bit 2
SHCORE0
0
Default Value : 0x00
bit 1
bit 0
SHARP1
SHARP0
0
0
[ LUMFIL1:LUMFIL0 ]-bit:
* This selects Luminance signal band limiting filters.
[ LUMFIL1:LUMFIL0]-bit
Filter
[ 00 ]
No band limiting filter
[ 01 ]
[ 10 ]
[ 11 ]
Narrow
MID.
WIDE
Note
Frequency characteristic is same as the
decimation filter
-3dB@6.29MHz
-3dB@2.94MHz
-3dB@3.3MHz
-3dB@4MHz
MS0244-E-03
31
Confidential
2005 / 07