參數(shù)資料
型號: 935077580157
廠商: NXP SEMICONDUCTORS
元件分類: 消費家電
英文描述: SPECIALTY CONSUMER CIRCUIT, PQFP80
封裝: PLASTIC, SOT-318, QFP-80
文件頁數(shù): 30/30頁
文件大?。?/td> 230K
代理商: 935077580157
1996 Oct 25
9
Philips Semiconductors
Preliminary specication
Progressive scan-Zoom and Noise
reduction IC (PROZONIC)
SAA4990H
Noise and cross-colour reduction
The noise reduction is field recursive with an average ratio
between fresh and over previous fields averaged
luminance and chrominance.
Two operating modes can be used in principal: the fixed
and the adaptive mode (see Table 6).
In the fixed mode, the averaging produces a constant
linear combination of the inputs. Except for k = 1, the fixed
mode should not be used for normal operation, because of
its smearing effects.
In the adaptive mode, the averaging ratio switches softly
on the basis of absolute differences in luminance among
the inputs. When the absolute difference is low, only a
small part of the fresh data will be added. When the
difference is high, much of the fresh data will be taken.
This occurs in either the situation of movement or where a
significant vertical contrast is seen.
To latter remark, note that recursion is done over a field,
and the pixel positions one field apart always have a
vertical offset of one frame line. So averaging is not only
done in the dimension of time but also in the vertical
direction. Therefore averaging vertically on e.g. a vertical
black to white edge would provide a grey result if this was
not adapted for.
The averaging in chrominance is slaved to the luminance
averaging. This implies that differences in the
chrominance are not taken into account for the k-factor
setting.
The noise reduction scheme effectively decreases both
noise and cross-colour patterns.
The cross-colour pattern does not produce an increase of
the measured luminance difference, therefore this pattern
will be averaged over many fields.
Fig.6 Noise reduction scheme.
(1) Yout =YA × k+YB × (1 k).
(2) see Table 9.
(3) see Fig.11.
handbook, full pagewidth
MGE029
FIELD
MEMORY
TF2
TF1
FILTER
LIMITER
FILTER
MULTIPLIER
(2)
k-CURVE
(3)
Yout
(1)
YA
YB
k
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