SAA7144HL Datasheet, PDF (16/64 Pages) NXP Semiconductors – Quadruple video input processor

Philips Semiconductors
SAA7144HL
Quadruple video input processor
8.4 Luminance processing
The 9-bit luminance signal, a digital CVBS format, is fed through a switchable prefilter.
High frequency components are emphasized to compensate for loss. The following
chrominance trap filter (f₀ = 4.43 MHz or 3.58 MHz center frequency set according to the
selected color standard) eliminates most of the color carrier signal. It can be bypassed via
I²C-bus bit BYPS (subaddress 09h, bit 7).
The high frequency components of the luminance signal can be peaked (control for
sharpness improvement via I²C-bus subaddress 09h, see Table 33) in two band-pass
filters with selectable transfer characteristic. This signal is then added to the original
(unpeaked) signal. For the resulting frequency characteristics see Figure 11 to Figure 16.
A switchable amplifier achieves common DC amplification, because the DC gains are
different in both chrominance trap modes. The improved luminance signal is fed to the
BCS control located in the chrominance processing block; see Figure 17.
18
V_Y
(dB)
(1)
6
(2)
(4)
(3)
−6
−18
mgd139
(1)
(2)
(4)
(3)
−30
0
2
4
6
8
f_Y (MHz)
(1) 43h
(2) 53h
(3) 63h
(4) 73h
Fig 11. Luminance control SA 09h, 4.43 MHz trap, prefilter on, different aperture
band-pass center frequencies.
9397 750 14454
Product data sheet
Rev. 01 — 21 April 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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