Television – Image signal processing circuitry specific to television – Special effects
Reexamination Certificate
1998-12-02
2004-11-23
Yenke, Brian P. (Department: 2614)
Television
Image signal processing circuitry specific to television
Special effects
C348S590000, C348S598000, C348S599000, C348S646000, C348S660000
Reexamination Certificate
active
06822694
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a signal processing apparatus suitable for use in a television set.
2. Description of the Related Art
A block diagram of a conventional signal processing apparatus is shown in FIG.
1
. First in
FIG. 1
, a text signal or a personal computer signal (hereinafter, simply referred to a text signal) of characters or the like comprising analog luminance signal Y and color difference signals U and V is inputted from input terminals
51
Y,
51
U, and
51
V. The inputted luminance signal Y and color difference signals U and V are supplied to A/D converters
52
Y,
52
U, and
52
V. In the A/D converters
52
Y,
52
U, and
52
V, the supplied luminance signal Y and color difference signals U and V are converted into digital signals at predetermined sampling frequencies and the text signal of the digital component signals is supplied to a text signal processing circuit
53
. A ratio of the sampling frequencies in the A/D converters
52
Y,
52
U, and
52
V is set to (Y:U:V)=(4:4:4).
A field memory
54
is connected to the text signal processing circuit
53
. In the text signal processing circuit
53
, predetermined signal processes are performed to the luminance signal Y and color difference signals U and V. The signal processed luminance signal Y and color difference signals U and V are supplied to a mixing circuit
55
.
A video signal comprising the analog luminance signal Y and color difference signals U and V is inputted from input terminals
56
Y,
56
U, and
56
V. The inputted luminance signal Y and color difference signals U and V are supplied to A/D converters
57
Y,
57
U, and
57
V. In the A/D converters
57
Y,
57
U, and
57
V, the supplied luminance signal Y and color difference signals U and V are converted into digital signals at predetermined sampling frequencies. A video signal of digital component signals is supplied to a video signal processing circuit
58
. A ratio of the sampling frequencies in the A/D converters
57
Y,
57
U, and
57
V is set to (4:1:1) or (4:2:2).
A field memory
59
is connected to the video signal processing circuit
58
. In the video signal processing circuit
58
, predetermined signal processes are performed to the luminance signal Y and color difference signals U and V. The signal processed luminance signal Y and color difference signals U and V are supplied to the mixing circuit
55
.
In the mixing circuit
55
, the text signal of (4:4:4) and the video signal of (4:1:1) or (4:2:2) are, for instance, switched and mixed. An output of the mixing circuit
55
is supplied to D/A converters
60
Y,
60
U, and
60
V.
In the D/A converters
60
Y,
60
U, and
60
V, the luminance signal Y and color difference signals U and V are converted into analog signals. The analog luminance signal Y and color difference signals U and V are supplied to LPFs (low pass filters)
61
Y,
61
U, and
61
V. In the LPFs
61
Y,
61
U, and
61
V, filter processes are performed to the luminance signal Y and color difference signals U and V in order to remove unnecessary signals. The filter processed luminance signal Y and color difference signals U and V are outputted from output terminals
62
Y,
62
U, and
62
V.
To clearly display characters, in the text signal, it is assumed that the color difference signals U and V and luminance signal Y have a similar band. Therefore, the ratio of the sampling frequencies is set to (4:4:4). On the other hand, in the video signal, a ratio of the sampling frequencies is set to (4:1:1) or (4:2:2) because the band of the color difference signals is narrower than that of the luminance signal Y. Thus, the capacity of the memory that is necessary for the signal processes can be saved. For the purpose of commonly using the D/A converter, two signals of the text signal of (4:4:4) and the video signal of (4:1:1) or (4:2:2) are mixed by digital signals prior to D/A converting. The band of the LPF after the D/A converter is matched with the band of the text signal together with the luminance signal Y and color difference signals U and V.
However, in the conventional system, since the band of the LPF at the post stage of the D/A converter is set to the wide band according to the band on the text signal side, the high frequency components (the harmonics components) of the color difference signals on the video signal side cannot be sufficiently attenuated. For example, as shown in
FIG. 2
, there is a problem such that oblique color edges which draw a diagonal line become a stairway shape.
On the other hand, if the band of the LPF is matched with the narrow band of the color difference signal of the video signal, since the high component of the text signal is eliminated, the color difference signals of the text signal become dull and there is a problem such that a color blur occurs and it is very hard to read the text.
OBJECTS AND SUMMARY OF THE INVENTION
It is, therefore, the invention to provide a signal processing apparatus to which a band limiting filter which can sufficiently attenuate the high frequency components of the color difference signals of the video signal is applied.
The invention is provided a signal processing apparatus for mixing a first digital component signal and a second digital component signal in which a sampling frequency of a color component is lower than that of the first digital component signal, characterized by comprising: a digital filter for performing a band limitation to the color component of the second digital component signal; mixing means for mixing the first digital component signal and the second digital component signal; D/A converting means for D/A converting an output of the mixing means; and a filter for performing a band limitation to an analog signal converted by the D/A converting means.
According to the invention, the high frequency components are removed from the color difference signals of the video signal (second digital component signal) of the ratio of the sampling frequencies of (4:2:2) or (4:1:1) by using a digital band limiting filter. After that, those signals are mixed and the mixed signal is D/A converted. Therefore, even if the band of the LPF at the post stage of the D/A converter is set to the wide band according to that of the text signal or the personal computer signal (first digital component signal) of the ratio of the sampling frequencies of (4:4:4), the oblique color edges are smoothly displayed.
The above, and other, objects, features and advantage of the present invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings.
REFERENCES:
patent: 5159453 (1992-10-01), Dhein et al.
patent: 5534942 (1996-07-01), Beyers, Jr. et al.
patent: 5550597 (1996-08-01), Wada et al.
patent: 5568204 (1996-10-01), Takamori
patent: 5712687 (1998-01-01), Naveen et al.
patent: 5745186 (1998-04-01), Shimizu et al.
patent: 5969767 (1999-10-01), Ishikawa et al.
patent: 5982455 (1999-11-01), Steele et al.
patent: 6061099 (2000-05-01), Hostetler
patent: 6188730 (2001-02-01), Ngai et al.
patent: 6307592 (2001-10-01), Go
patent: 0862334 (1998-02-01), None
patent: 0921693 (1999-06-01), None
Kojima Hiroyuki
Miyazaki Shinichiro
Shirahama Akira
Sugaya Hiroshi
Frommer William S.
Frommer & Lawrence & Haug LLP
Sony Corporation
Yenke Brian P.
LandOfFree
Signal processing apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Signal processing apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Signal processing apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3309832