SAA7108AE Datasheet, PDF (48/208 Pages) NXP Semiconductors – HD-CODEC

NXP Semiconductors
SAA7108AE; SAA7109AE
HD-CODEC
9.1.3.2 Luminance path
The rejection of the chrominance components within the 9-bit CVBS or Y input signal is
achieved by subtracting the remodulated chrominance signal from the CVBS input.
The comb filtered C_B-C_R components are interpolated (upsampled) by the low-pass 3
block. Its characteristic is controlled by LUBW (subaddress 09h, bit 4) to modify the width
of the chrominance ‘notch’ without influencing the chrominance path. The programmable
frequency characteristics available, in conjunction with the LCBW2 to LCBW0 settings,
can be seen in Figure 22 to Figure 25. It should be noted 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 center frequency of the notch is automatically adapted to the chosen
color standard.
The interpolated C_B-C_R 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 remodulated 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 Figure 26. 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).
SAA7108AE_SAA7109AE_3
Product data sheet
Rev. 03 — 6 February 2007
© NXP B.V. 2007. All rights reserved.
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