參數(shù)資料
型號(hào)： SAA4979H
廠商： NXP SEMICONDUCTORS
元件分類(lèi)： 消費(fèi)家電
英文描述： Sample rate converter with embedded high quality dynamic noise reduction and expansion port
中文描述： SPECIALTY CONSUMER CIRCUIT, PQFP128
封裝： 28 X 28 X 3.40 MM, PLASTIC, QFP-128
文件頁(yè)數(shù)： 17/52頁(yè)
文件大?。?/td> 224K
代理商： SAA4979H
2002 May 28
17
Philips Semiconductors
Product specification
Sample rate converter with embedded high quality
dynamic noise reduction and expansion port
SAA4979H
7.3.3
P
ANORAMIC ZOOM
The panoramic zoom block contains a second sample rate
converter, which performs the following tasks:
Linear horizontal sample rate conversion in both zoom
and compress direction, with a sample rate conversion
factor between 0 and 2, meaning infinite zoom up to a
compression with a factor of 2
Dynamic sample rate conversion e.g. for panorama
mode display of 4 : 3 material on a 16 : 9 screen.
For linear horizontal zoom or compression the sample rate
conversion factor is static during a video line (control
input: c0). Positive values of c0 are suitable for
compression, negative values result in expansion.
In panorama mode the video lines are geometrically
expanded towards the sides. The sample rate conversion
factor is modulated along the video line. A parabolic shape
of the sample rate conversion factor can be obtained with
the parameter c2, which controls the second order
variation of the sample rate. Negative values of c2 are
suitable for panorama mode, positive values result in the
inverse mode (amaronap mode).
The panoramic zoom block also provides a dynamically
controlled delay with an accuracy up to
1
64
of a pixel and
a range of
0.5 to +0.5 lines (control input: hshift).
Sufficient accuracy in interpolation for phase positions
between the original samples is achieved with a variable
phase delay filter with 10 taps for luminance signals and
6 taps for chrominance signals.
7.3.4
D
IGITAL COLOUR TRANSIENT IMPROVEMENT
The Digital Colour Transient Improvement (DCTI) is
intended for U and V signals originating from a 4 : 1 : 1
source. Horizontal transients are detected and enhanced
without overshoots by differentiating, make absolute and
again differentiating the U and V signals separately. This
results in a 4 : 4 : 4 U and V bandwidth. To prevent
third-harmonic distortion, which is typical for this
processing, a so called over the hill protection prevents
peak signals becoming distorted.
It is possible to control the following settings via the
microcontroller: gain width (see Fig.10), threshold (i.e.
immunity against noise), selection of simple or improved
first differentiating filter (see Fig.9), limit for pixel shift
range (see Fig.11), common or separate processing of
U and V signals, hill protection mode (i.e. no
discolourations in narrow colour gaps), low-pass filtering
for U and V signals (see Fig.12) and a so called super hill
mode, which avoids discolourations in transients within a
colour component.
7.3.5
HORIZONTAL SMART
Y
PEAKING
A linear peaking is applied, which amplifies the luminance
signal in the middle and the upper ranges of the
bandwidth.
The filtering is an addition of:
The original signal
The original signal high-passed with maximum gain at a
frequency of
1
2
f
s
(sample frequency f
s
= 32 MHz)
The original signal band-passed with a centre frequency
of
1
4
f
s
The original signal band-passed with a centre frequency
of 4.76 MHz.
The band-passed and high-passed signals are weighted
with the factors 0,
1
16
,
2
16
,
3
16
,
4
16
,
5
16
,
6
16
and
8
16
,
resulting in a maximum gain difference of 2 dB per step at
the centre frequencies.
Coring is added to avoid amplification of low amplitudes in
the high-pass and band-pass filtered signals, which are
considered to be noise. The coring threshold can be
programmed as 0 (off),
±
4,
±
8,
±
12 to
±
60 LSB with
respect to the (signed) 10-bit signal.
In addition the peaking gain can be reduced depending on
the signal amplitude, programming range 0 (no
attenuation),
1
4
,
2
4
and
4
4
. It is also possible to make
largerundershootsthanovershoots,programmingrange 0
(no attenuation of undershoots),
1
4
,
2
4
and
4
4
.
A steepness detector is built-in, which provides
information for dynamic control of the peaking. For that the
maximum absolute value of the band-pass filtered signal
within a video field is calculated and can be read out by the
microcontroller (control output: steepness_max).
7.3.6
N
ON
-
LINEAR PHASE FILTER
The non-linear phase filter adjusts possible group delay
differences in the Y, U and V output channels. The filter
coefficients are: [
λ ×
(1
μ
); 1 +
λ
;
λ × μ
] where
λ
determinesthestrengthofthefilterand
μ
determinesthe
asymmetry. The effect of the asymmetry is a decrease in
the delay for higher frequencies with
μ ≤
0.5. Control
settings are provided for
λ
= 0,
1
8
,
2
8
,
3
8
and
μ
= 0,
1
4
,
1
2
.
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