SDA9288X Datasheet, PDF (13/46 Pages) Siemens Semiconductor Group – Single Chip PIP System

SDA 9288X
2.2 Input Signal Processing
This stage performs the decimation of the inset signal by horizontal and vertical filtering
and sub-sampling. A special antialias filter improves the frequency response of the
luminance channel. It is optimized for the use of the horizontal decimation factor 3:1.
A window signal, derived from the sync pulses and the detected line standard, defines
the part of the active video area used for decimation. For HSIDEL = ‘0’ the decimation
window is opened about 104 clock periods (13.5 MHz) after the horizontal
synchronization pulse. For the 625 lines standard the 36th video line is the first
decimated line, for the 525 lines standard decimation starts in the 26th video line.
The following filters are implemented:
Horizontal Decimation
3:1
3:1
4:1
4:1
Component
Luminance
Chrominance
Luminance
Chrominance
Filter
1 + z^{– 1} + z^{– 2}
1 + 2 × z^{– 1} + z^{– 2}
1 + z^{– 1} + z^{– 2}+ z^{– 3}
1 + z^{– 1} + z^{– 2}+ z^{– 3}
Vertical Decimation
Component
Filter
3:1
Luminance
1 + z^{– L} + z^{– 2L}
3:1
Chrominance
1 + 2 × z^{– L} + z^{– 2L}
4:1
Luminance
1 + z^{– L} + z^{– 2L}+ z^{– 3L}
4:1
Chrominance
1 + z^{– L} + z^{– 2L}+ z^{– 3L}
z = e^jωT,T = 1/13.5 MHz for luminance T = 1/3.375 MHz for chrominance
L = samples per line for luminance respectively chrominance
The realized chrominance filtering allows omitting the color decoder delay line for PAL
and SECAM demodulation if the color decoder supplies the same output voltages
independent of the kind of operation. In case of SECAM signals an amplification of the
chrominance signals by a factor of 2 is necessary because just every second line a
signal is present. This chrominance amplification is programmable via pin SYS or
I²C Bus (AMSEC).
The horizontal and vertical decimation factors are free programmable (DECHOR,
DECVER). Using different decimations horizontal and vertical 16:9 applications become
realizable:
DECHOR = ‘1’, DECVER = ‘0’: picture size 1/9 for 4:3 inset signals on 16:9 displays
DECHOR = ‘0’, DECVER = ‘1’: picture size 1/16 for 16:9 inset signals on 4:3 displays
Semiconductor Group
13
03.96