PAL/NTSC/SECAM video decoder with adaptive PAL/NTSC comb ...

Philips Semiconductors
PAL/NTSC/SECAM video decoder with adaptive PAL/NTSC
comb filter, VBI-data slicer and high performance scaler
Preliminary specification
SAA7114H
8.1.3.2 Luminance path
The rejection of the chrominance components within the
9-bit CVBS or Y input signal is done by subtracting the
re-modulated chrominance signal from the CVBS input.
The comb filtered UV-components are interpolated
(upsampled) by the low-pass 3 block. It’s characteristic is
controlled by LUBW (subaddress 09H, bit 4) to modify the
width of the chrominance ‘notch’ without influence to the
chrominance path. The programmable frequency
characteristics available in conjunction with the
LCBW2 to LCBW0 settings can be seen in Figs 12 to 15.
Note that these frequency curves are only valid for Y-comb
disabled filter mode (YCOMB = 0). in comb filter mode the
frequency response is flat. The centre frequency of the
notch is automatically adapted to the chosen colour
standard.
The interpolated UV-samples are multiplied by two
time-multiplexed subcarrier signals from the subcarrier
generation block 2. This second DTO is locked to the first
subcarrier generator by an increment delay circuit
matched to the processing delay, which is different for
PAL and NTSC standards according to the chosen comb
filter algorithm. The two modulated signals are finally
added to build the re-modulated chrominance signal.
The frequency characteristic of the separated luminance
signal can be further modified by the succeeding
luminance filter block. It can be configured as peaking
(resolution enhancement) or low-pass block by
LUFI3 to LUFI0 (subaddress 09H, bits 3 to 0). The 16
resulting frequency characteristics can be seen in Fig.16.
The LUFI3 to LUFI0 settings can be used as a user
programmable sharpness control.
The luminance filter block also contains the adjustable
Y-delay part; programmable by YDEL2 to YDEL0
(subaddress 11H, bits 2 to 0).
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