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參數(shù)資料
| 型號： | SAA4956TJ |
| 廠商： | NXP SEMICONDUCTORS |
| 元件分類： | 存儲器 |
| 英文描述： | 2.9-Mbit field memory with noise reduction |
| 中文描述： | SPECIALTY MEMORY CIRCUIT, PDSO40 |
| 封裝： | PLASTIC, SOJ-40 |
| 文件頁數(shù)： | 12/36頁 |
| 文件大小： | 243K |
| 代理商： | SAA4956TJ |
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1998 Dec 08
12
Philips Semiconductors
Preliminary specification
2.9-Mbit field memory with noise reduction
SAA4956TJ
The main function of the noise reduction is shown in Fig.3.
It is divided in two signal paths for chrominance and
luminance. Two operating modes can be used in principal:
the fixed and the adaptive mode. In both modes the
applied frequency range, where the noise reduction takes
place, can be reduced or not reduced (I
2
C-bus control:
unfiltered).
The noise reduction operates field recursive with an
average ratio between fresh (new) and over previous fields
averaged (old) luminance and chrominance. Noise
reduction can be activated by forcing the NREN control
signal to HIGH. In this case the system starts with default
settings for noise reduction and noise shape, if clock is
applied to SWCK. If NREN is LOW the noise reduction
block is bridged via a data mux (see Fig.1). During NREN
HIGH, only half of the write frequency, which is allowed
during NREN LOW, can be applied. This is explained by
the need for a second memory read access (READ2) to
get old data (D-field delay) in the same frequency as the
write frequency. The noise reduction is controlled via
I
2
C-bus settings. Since the PAN-IC (SAA4995WP) needs
approximately the same write frequency as the read
frequency for the noise reduction option (32 MHz), a
deactivated self-refresh is required. This setting can be
done via the I
2
C-bus interface (I
2
C-bus control:
no_refresh).
In the fixed mode, the noise reduction produces a constant
weighted input averaging. Because of smearing effects
this mode should not be used for normal operation except
for K = 1. The fixed mode can be activated separately for
chrominance (I
2
C-bus control: chromafix) and luminance
(I
2
C-bus control: lumafix).
In the adaptive mode, the averaging ratio (K-factor) is
based on the absolute differences of luminance
respectively chrominance among the inputs. When the
absolute difference is low, only a small part of the fresh
data will be added. In cases of high difference, much of
fresh data will be taken. This occurs in either situation of
movement or where a significant vertical contrast is seen.
The relation between the amount of movement and the
K-factor values is defined via a Look-Up Table (LUT)
where the steps can be programmed (I
2
C-bus controls:
Ksteps).
It should be noted that recursion is done over fields, and
that pixel positions between the new and old fields always
have a vertical offset of one 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 a white edge would provide a grey result.
The averaging in chrominance can be slaved optionally to
the luminance averaging (I
2
C-bus control:
Klumatochroma), therefore chrominance differences are
not taken into account for the K-factor setting of the
chrominance signal path.
The noise reduction scheme effectively also decreases the
cross-colour patterns if for the averaging in chrominance
the adaptive noise reduction is slaved to the luminance
averaging (I
2
C-bus control: Klumatochroma).
The cross-colour pattern does not produce an increase of
the measured luminance difference, therefore this pattern
will be averaged over many fields.
7.2.1
R
EFORMATTING AND FORMATTING
The standard applications are using the 4 : 1 : 1 YUV data
stream (see Table 1). The noise reduction processing
uses internally the 4 : 2 : 2 data stream. An up converter to
4 : 2 : 2 is applied with a linear interpolation filter for
creation of the extra samples. These are combined with
the original samples from the 4 : 1 : 1 stream. Instead of
the 4 : 1 : 1 mode the input or output colour can be
handled as DPCM format which is a certain data
compression (I
2
C-bus control: DPCMin, DPCMout) if the
4 : 2 : 2 data bandwidth is needed e.g. for applications
together with SAA4978H. The incoming colour data can be
also inverted for special purposes (I
2
C-bus control:
Chroma_inverted).
Table 1
Digital input and output bus format
4 : 1 : 1 FORMAT
INPUT
PIN
Y07
Y06
Y05
Y04
Y03
Y02
Y01
Y00
U07
U06
V07
V06
Y17
Y16
Y15
Y14
Y13
Y12
Y11
Y10
U05
U04
V05
V04
Y27
Y26
Y25
Y24
Y23
Y22
Y21
Y20
U03
U02
V03
V02
Y37
Y36
Y35
Y34
Y33
Y32
Y31
Y30
U01
U00
V01
V00
D11
(Y7)
D10
(Y6)
D9
(Y5)
D8
(Y4)
D7
(Y3)
D6
(Y2)
D5
(Y1)
D4
(Y0)
D3
(U1)
D2
(U0)
D1
(V1)
D0
(V0)
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SAA4960 | Integrated PAL comb filter |
| SAA4963 | Integrated NTSC comb filter |
| SAA4963T | Integrated NTSC comb filter |
| SAA4970T | Economical video processing IC ECOBENDIC |
| SAA4974 | Besic without ADC |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SAA4960 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Integrated PAL comb filter |
| SAA4963 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Integrated NTSC comb filter |
| SAA4963T | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Integrated NTSC comb filter |
| SAA4970T | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Economical video processing IC ECOBENDIC |
| SAA4974 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Besic without ADC |
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