EP0501728A2
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Gradation corrector
Assignee: Panasonic Holdings Corp
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Filing: 1992-02-24
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Granted: —
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Expires: 2012-02-24
Abstract
Abstract In a gradation corrector used in a television receiver, a clipping circuit (51) is connected to an output of a histogram memory (2) and a clipping level of the clipping circuit (51) is changed in accordance with an output of an S/N detecting circuit (50). Thereby, when the minimum value is detected, it is possible to prevent a large variation of the value to be detected which may be caused from noise or the like. Also, a circuit (52) for detecting a change in video scene and a recursive filter circuit composed of an adder (53) and a xK circuit (54) (and a two-input/one-output selector circuit (55)) are provided on the output side of a clipping circuit (51) and the coefficient value K of the xK circuit (54) (or the selector circuit (55) is controlled in accordance with an output of the video scene change detecting circuit (52). Thereby, it is possible to make a smooth gradation correction which is not affected by noises or the like (or to make a gradation correction with rapid response which follows a change in video scene).
Inventors
- 👤 Toshiaki Tsuji
- 👤 Atsuhisa Kageyama
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 13:11
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/90; G06T5/92; G06T5/40; H; H04; H04N; H04N19/00; H04N19/10; H04N19/134; H04N19/142; H04N19/169; H04N19/179; H04N19/85; H04N19/87; H04N5/00; H04N5/14; H04N5/147; H04N5/20
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
234 words
A gradation corrector comprising a histogram memory (2) for storing a histogram of a video luminance signal, a histogram operating circuit (3) connected to the histogram memory for extracting a feature of the histogram from data stored in the histogram memory, a limiter/adder circuit (5) connected to an output of the histogram operating circuit for processing the data of the histogram memory, an accumulation control register circuit (6) and a normalization control register circuit (7) each connected to an output of the histogram operating circuit, a histogram accumulation circuit (8) connected to the histogram memory and the accumulation control register circuit for making a cumulative addition for the processed data of the histogram memory, a cumulative histogram memory (9) for storing the result of cumulative addition, a look-up table operating circuit (10) connected to the cumulative histogram memory and the normalization control register circuit for normalizing data of the cumulative histogram memory, and a look-up table memory (11) for storing the result of normalization, the histogram operating circuit including a circuit for detecting the minimum value of the histogram; the minimum value detecting circuit having a circuit (50) for detecting S/N from an input video signal and a clipping circuit (51) connected to an output of the S/N detecting circuit and an output of the histogram memory, a clipping level of the clipping circuit being controlled by the output of the S/N detecting circuit.
Claim 2
Dependent Claim
237 words
A gradation corrector comprising a histogram memory for storing a histogram of a video luminance signal, a histogram operating circuit connected to the histogram memory for extracting a feature of the histogram from data stored in the histogram memory, a limiter/adder circuit connected to an output of the histogram operating circuit for processing the data of the histogram memory, an accumulation control register circuit and a normalization control register circuit each connected to an output of the histogram operating circuit, a histogram accumulation circuit connected to the histogram memory and the accumulation control register circuit for making a cumulative addition for the processed data of the histogram memory, a cumulative histogram memory for storing the result of cumulative addition, a look-up table operating circuit connected to the cumulative histogram memory and the normalization control register circuit for normalizing data of the cumulative histogram memory, and a look-up table memory for storing the result of normalization, the histogram operating circuit including a circuit for detecting the minimum value of the histogram, the minimum value detecting circuit having a circuit (52) connected to a clipping circuit (51) for detecting a change in video scene, a recursive filter circuit composed of an adder (53) and a circuit (54) for making a multiplication by a certain coefficient K, and a circuit for controlling the xK circuit of the recursive filter circuit by an output of the video scene change detecting circuit.
Claim 3
Dependent Claim
251 words
A gradation corrector comprising a histogram memory for storing a histogram of a video luminance signal, a histogram operating circuit connected to the histogram memory for extracting a feature of the histogram from data stored in the histogram memory, a limiter/adder circuit connected to an output of the histogram operating circuit for processing the data of the histogram memory, an accumulation control register circuit and a normalization control register circuit each connected to an output of the histogram operating circuit, a histogram accumulation circuit connected to the histogram memory and the accumulation control register circuit for making a cumulative addition for the processed data of the histogram memory, a cumulative histogram memory for storing the result of cumulative addition, a look-up table operating circuit connected to the cumulative histogram memory and the normalization control register circuit for normalizing data of the cumulative histogram memory, and a look-up table memory for storing the result of normalization, the histogram operating circuit including a circuit for detecting the minimum value of the histogram, the minimum value detecting circuit having a circuit (52) connected to a clipping circuit (51) for detecting a change in video scene, a recursive filter circuit composed of an adder (53) and a circuit (54) for making a multiplication of a certain coefficient K, and a two-input/one-output selector (55) circuit for making a change-over between an output of the recursive filter circuit and an output of the clipping circuit in accordance with an output of the video scene change detecting circuit.
References Cited (Backward Citations)
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