Television – Format conversion – Line doublers type
Reexamination Certificate
2001-04-11
2004-02-17
Hsia, Sherrie (Department: 2614)
Television
Format conversion
Line doublers type
C348S620000, C348S700000
Reexamination Certificate
active
06693676
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motion adaptive YC separation apparatus for separating a luminance signal (hereinafter referred to as Y-signal or simply as Y) and a color signal (hereinafter referred to as C signal or simply as C) from a composite television signal (hereinafter referred to as V-signals) in which the color signal is frequency multiplexed on the high frequency area of the luminance signal, and more specifically, to a motion detecting apparatus suitable for detecting the motion in a motion adaptive scan-line interpolating apparatus for converting the television signal from interlace scan to sequential scan.
2. Description of the Related Art
Many improvements have been made for a motion adaptive process aiming at improvement of picture quality on the current color television. The motion adaptive process means a process to detect the motion of the picture locally by the motion detecting circuit and to switch-over between the still picture process that is suitable for the still picture and the moving picture process that is suitable for the moving picture adaptationally according to detected motions. The primary motion adaptive process in the current color television includes a motion adaptive YC separation process and a motion adaptive scan-line interpolation, and various signal process circuits for improving the picture quality by the use of a delay circuit having a delay time that is the same as the vertical scanning frequency of the television signal or higher (hereinafter simply referred to as delay circuit) has been proposed with the development of the mass storage digital memory.
In some of video signals that are transmitted or accumulated in the form of three system component signal including a luminance signal and two types of color difference signals used in, for example, a digital television broadcast or in consumer-oriented DVD players and that employ interlace scanning, a signal processing circuit that performs motion adaptive scan-line interpolation is used as described above.
In addition, when displaying a television signal of interlace scanning on the display device of dot matrix type such as a liquid crystal panel or a plasma display, there are cases where the signal processing circuit that performs motion adaptive scan-line interpolation is used.
The motion adaptive YC separation process removes the cross component elements such as cross color or dot scroll completely by separating Y signal by taking sum of the frames and C signal by taking difference between the frames when it is determined to be a still picture in accordance with the amount of the motion detected by the motion detecting circuit. When it is determined to be a moving picture, Y signal and C signal are separated by intra-field process.
The motion adaptive scan-line interpolating process performs the inter-field interpolation to remove line flickers when it is determined to be a still picture according to the amount of motion detected by the motion detecting circuit in the same manner as described above, for the purpose of converting interlace signal to sequential scan signal. When it is determined to be a moving picture, inter-field interpolation is performed.
The accuracy of motion detection of the motion detecting circuit in the above-described motion adaptive process has a significant effect on the quality of reproduced picture. The error in motion detection may be classified into two types as follows.
(1) Detection Error: a part of a still picture is determined to be a moving picture and moving picture process is performed.
(2) Detection failure: a part of a moving picture is determined to be a still picture and still picture process is performed.
Out of these two types of errors, “Detection failure” deteriorates the picture quality significantly, and thus the motion detecting circuit that prevents detection failures as much as possible has been proposed.
FIG. 9
is a block circuit diagram showing an example of the motion detecting circuit in the related art shown in Japanese Patent Laid-Open No. 90987/1988. This example is based on the premise that input signal is V-signal.
In
FIG. 9
, NTSC (National Television System Committee) system analogue V-signal incoming through the input terminal
1
is converted into a digital signal at analogue/digital conversion circuit (hereinafter referred to as ADC)
2
. The digitized V-signal is fed to the first detecting circuit
3
to detect the motion of the Y-signal low frequency component. In the first detecting circuit
3
, digitized V-signal is fed to the first frame memory
4
and then a signal delayed by one frame and a signal fed into the frame memory
4
are supplied to the subtraction circuit
5
to obtain a difference signal across one frame. Then, the output signal from the subtraction circuit
5
is fed to the low-pass filter (hereinafter referred o as LPF)
6
to remove the color signal band, so that motion information of Y-signal low pass component can be obtained in the output of LPF
6
. At this time, it is determined to be a still picture when the output of LPF
6
is zero, and to be a moving picture when the output is the value other than zero. The output signal of LPF
6
has polarities of plus and minus, it is fed to the absolute value circuit
7
to obtain an absolute value. The output of the absolute value 7 is a conversion circuit
8
, and is converted into non-linear shape by the I/O characteristics as shown in
FIG. 10
, and input of low level is converted into the output of zero to remove the noise effect.
On the other hand, a digitized V-signal from ADC
2
is fed to the band-pass filter (hereinafter referred to as BPF)
9
to obtain a signal in color signal band. By the action of ACC operated so as to maintain the level of burst signal contained in the output signal of BPF
9
constant, the output of the amplification circuit
10
for ACC contains a constant signal in which the variation of color signal level caused by the frequency characteristics of the transmission path is corrected. Thereafter, the color signal is demodulated by demodulation circuit
11
, which works to cancel the inversion of the phase of the color width carrier between frames. The output of the demodulation circuit
11
is fed to the second detecting circuit
12
to detect the motion of the signal in the color signal band.
In the first place, the output signal of the modulation circuit
11
is fed to the second frame memory
13
to delay by one frame, and then fed to the third frame memory
14
to delay by another frame. Then, the output signal of the demodulation circuit
11
and the signal delayed by two frames by the frame memories
13
and
14
are fed to the subtraction circuit
15
to obtain the difference signal across two frames. Two signals two frames away from each other are identical in the phase of high frequency components of Y-signal and C-signal. In the case of a still picture, the difference across two frames is zero, and thus when the difference signal across two frames is a value other than zero, it is determined to be a moving picture. Moreover, the absolute value circuit
16
and the conversion circuit
17
operate in the same manner as the absolute circuit
7
and the conversion circuit
8
respectively.
The output signals of the first detecting circuit
3
and of the second detecting circuit
12
described above are combined by feeding them to the combining circuit
18
. Thereby, the output of the combining circuit
18
contains motion information of signals across the whole band of V-signal. The combining circuit
18
can be implemented by selecting a lager signal out of two input signals.
By feeding the output signal of the combining circuit
18
into the spatio-temporal filter circuit
19
and using motion information of certain pixels being spatio-temporally around a certain pixel together, erroneous detection of rapid motion of the object is prevented. In the spatio-temporal filter circuit
19
, the output signal of the combining circuit
18
and the output
Hanai Masaaki
Okumura Akira
Yamaguchi Noriyuki
Birch & Stewart Kolasch & Birch, LLP
Hsia Sherrie
Mitsubishi Denki & Kabushiki Kaisha
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