Television – Image signal processing circuitry specific to television – Chrominance-luminance signal separation
Reexamination Certificate
1998-02-19
2001-09-11
Eisenzopf, Reinhard J. (Department: 2614)
Television
Image signal processing circuitry specific to television
Chrominance-luminance signal separation
C348S665000, C348S669000, C348S670000
Reexamination Certificate
active
06288754
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a YC separation circuit for separating an input composite video signal into a carrier chrominance signal (chrominance signal) and a luminance signal.
2. Description of the Prior Art
A YC separation circuit for separating an input composite video signal into a carrier chrominance signal and a luminance signal is known.
FIG. 6
shows a block diagram of such a prior art YC separator. In the three-dimensional YC separator shown in
FIG. 6
, a color video signal (a composite video signal) in which a luminance signal and a carrier chrominance signal are multiplexed in a common band is supplied to an inter-frame YC separation circuit
81
and an inter-line YC separation circuit
82
where YC separation is performed using correlation between frames and correlation between lines respectively. The separated luminance signal and the separated carrier chrominance signals are supplied to the selector
83
. The selector
83
outputs an output from either the output of the inter-frame YC separation circuit
81
or the output of the inter-line YC separation circuit
82
in accordance with a motion detection from a motion detection circuit
84
.
FIG. 7
is a block diagram partially showing the prior art inter-frame YC separation circuit
81
shown in FIG.
6
. The inter-frame YC separation circuit
81
separates the input composite video signal and extracts a carrier chrominance signal from the input composite video signal. That is, the input composite video signal is supplied to a frame memory
85
and delayed by one frame there and then, subtraction between the delayed input composite video signal and the non-delayed input composite video signal and only the carrier chrominance signal is separated, extracted, and outputted by a subtractor
86
. Moreover, instead the subtractor
86
, an adder can separate and extract the luminance signal from the input composite video signal.
Return to
FIG. 6
again, the motion detection is performed by the motion detection circuit
84
on the basis of a frame difference signal of a low frequency components of the luminance signal outputted from the inter-frame YC separation circuit
81
. The selector
83
selects the luminance signal and the carrier chrominance signal outputted from the inter-frame YC separation circuit
81
when an image portion where the image stops, i.e., it is judged that there is almost no motion by the motion detection detection circuit
84
, and selects the luminance signal and the carrier chrominance signal outputted from the inter-line YC separation circuit
82
when the image portion where the image moves, i.e., it is judged that there is a motion.
If the NTSC composite video signal is inputted to this circuit, because of its nature, in the case of the still picture, it is well known that the luminance signal can be perfectly separated by adding the video signal of the present frame to the video signal of one-frame previous frame and the carrier chrominance signal can be perfectly separated by subtraction between these signals. However, because this principle is not true to the image portion having a motion, it is necessary to switch to the intra-field (between lines, inter-line) YC separation to such an image including a motion. Therefore, the above-mentioned circuit structure requires a frame memory, so that a circuit scale becomes large. Then, to reduce a capacity of the frame memory
85
in
FIG. 7
, another prior art YC separator has been known, which further comprises a thinning circuit
87
on the input side of the frame memory
85
.
FIG. 8
is a block diagram of another prior art YC separator. In
FIG. 8
, the composite video signal to be supplied to the frame memory
85
is thinned and the output carrier chrominance signal of the subtractor
86
is interpolated by an interpolating circuit
88
.
Still another prior art YC separator where interpolation is effected in the direction showing strong correlation (upwardly, downwardly, the right direction, or the left direction) using three lines of the data (thinned video data) is also known (for example, Japanese patent application provisional publication No. 7-
154820).
FIG. 9
shows a block diagram of still another prior art YC separator disclosed in Japanese patent application provisional publication No. 7-154820. In
FIG. 9
, a composite video signal outputted from an input terminal
91
is sub-sampled in accordance with the cycle of the color sub-carrier by the sub-sampling circuit
92
. The sampled signal is delayed by one frame by a delay circuit
93
and supplied to a subtraction circuit
94
and directly supplied to the subtraction circuit
94
to obtain only the carrier chrominance signal through subtraction.
The carrier chrominance signal from the subtraction circuit
94
is supplied to a horizontal interpolation circuit
95
and to a vertical interpolation circuit
96
respectively, where data of the carrier chrominance signal having signal phase in horizontal and vertical directions lost by the sub-sampling are interpolated. Moreover, the output carrier chrominance signal from the subtraction circuit
94
and the composite video signal from the input terminal
91
are supplied to a correlation detection circuit
97
. The correlation detection circuit
97
detects which direction between the horizontal and the vertical direction data lost in the sub-sampling circuit
92
shows a stronger correlation in.
A selection circuit
98
selects the signal showing a stronger correlation from output signals from the subtraction circuit
94
, the horizontal interpolation circuit
95
, or the vertical interpolation circuit
96
. Therefore, the selection circuit
98
outputs the carrier chrominance signal with the lost data due to the sub-sampling interpolated. The output of the selection circuit
98
is supplied to an output terminal
101
and supplied to a subtraction circuit
100
where subtraction is effected between the composite signal time-adjusted by a delay circuit
99
and the carrier chrominance signal to output a luminance signal. The luminance signal is supplied to an output terminal
102
.
SUMMARY OF THE INVENTION
The aim of the present invention is to provide a novel YC separator.
According to the present invention there is provided a first YC separator comprising: a thinning circuit for thinning a composite video signal including a luminance signal and a carrier chrominance signal multiplexed in a common band in response to a sub-Nyquist sampling signal to output a thinned composite video signal; a first separation circuit for separating the carrier chrominance signal from the thinned composite video signal through inter-frame operation; a second separation circuit for separating the carrier chrominance signal from the composite video signal through intra-field operation; a first high frequency component detecting circuit for detecting a first high frequency component in the separated carrier chrominance signal from the first separation circuit; a second high frequency component detection circuit for detecting a second high frequency component in the carrier chrominance signal from the second separation circuit; a first interpolation circuit for generating a first interpolated carrier chrominance signal from the separated carrier chrominance signal from the first separation circuit at an interpolation timing defined by the sub-Nyquist sampling signal through linear-interpolating; a second interpolation circuit for selectively adding the detected second high frequency component to the first interpolated carrier chrominance signal in accordance with the detected first high frequency component to generate a second interpolated carrier chrominance signal; an outputting circuit for outputting the separated carrier chrominance signal from the first separation circuit at the timing corresponding to the sub-Nyquist sampling signal and the second interpolated carrier chrominance signal at the interpolation timing; and a luminance signal generation circuit for effecting subtraction between t
Connolly Bove Lodge & Hutz
Eisenzopf Reinhard J.
Tran Trang U.
Victor Company of Japan Ltd.
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