Matsushita Electric Industrial Co., Ltd.

Masahiro Takeshima

Atsuhisa Kageyama

Minoru Kawabata

Hiroko Sugimoto

Nobuo Taketani

Hiroshi Moribe

Hiroshi Ando

Ryuichi Shibutani

Hisao Morita

Masahiko Sasada

Koji Matsuhira

Yutaka Otani

A false contour correcting apparatus is capable of removing a false contour in an image based on a digital image signal while avoiding such a side effect caused by false contour correction where noises negatively effecting the display occur on a screen. Therefore, in the false contour correcting apparatus according, a double bit change detection circuit detects as a double bit change a signal value change which is twice a minimum quantization unit in a digital image signal, and outputs a double bit change detection signal representing the position of the double bit change. A signal correction circuit corrects the double bit change in the digital image signal into two one-bit changes on the basis of the double bit change detection signal. Consequently, a false contour corresponding to a portion where the double bit change exists is removed.

False contour correcting apparatus and method

The vertical/horizontal amplitude control device for controlling a vertical amplitude and a horizontal amplitude of an image display device for displaying a video signal includes a brightness level detector for detecting a brightness level of the video signal, a vertical amplitude controller for controlling the vertical amplitude based on the brightness level, and a horizontal amplitude controller for controlling the horizontal amplitude based on the brightness level. The device controls the vertical and horizontal amplitudes into constant without a delay from a change of a video signal even when the brightness level of the video signal abruptly changes.

Vertical/horizontal amplitude controller

The automatic cut-off system includes a video data processing circuit, a cut-off control circuit, a drive circuit, and a level control section. The video data processing circuit adds a cut-off reference pulse having a predetermined level to primary-color signals of red (R), green (G) and blue (B) at different timings within a single vertical blanking interval, and outputs latch timing signals respectively indicating the timings. The cut-off control circuit shifts a level of each primary-color signal having the cut-off reference pulse added thereto based on a corresponding cut-off control signal. The drive circuit drives each cathode of a CRT (cathode-ray tube) based on a corresponding one of the shifted primary-color signals, and outputs a voltage corresponding to each cathode current as a common feedback signal. The level control section latches the feedback signal in response to each latch timing signal, and outputs the cut-off control signal of one of the primary-color signals.

Automatic cut-off system

In a horizontal deflection circuit, a waveform response of a horizontal output pulse must be adequately taken into account before and after a switching of the horizontal output pulse so that the waveform does not lack in shape and does not lose continuity at the switching. A switching apparatus for a horizontal driving apparatus includes (a) a horizontal driving pulse generator which generates a horizontal driving pulse from a horizontal synchronization signal, (b) an alternative signal generator which outputs an alternative signal different from the horizontal driving pulse, (c) a horizontal output control device which determines a timing to switch between the horizontal driving pulse and the alternative signal, and (d) a switching device which switches an output pulse with a control signal which is output from the horizontal output control device. The switching device switches only when both the output signal from the horizontal driving pulse generator and the output signal from the alternative signal generator change from a low level to a high level at the same time.

Switching apparatus for horizontal driving pulse

A first motion detection circuit detects presence/absence of motion in an image on the basis of a composite video signal and an output signal of a frame memory. A three-dimensional Y/C separation circuit separates a luminance signal and a chrominance signal from the composite video signal by an inter-frame operation or an intra-frame operation on the basis of a motion signal output from the first motion detection circuit. A motion detection circuit detects presence/absence of motion in the image on the basis of the luminance signal output from the three-dimensional Y/C separation circuit. A synthesizing circuit synthesizes motion signals output from the first motion detection circuit and a second motion detection circuit. A three-dimensional noise reduction circuit reduces noise of the luminance signal output from the three-dimensional Y/C separation circuit by an inter-frame operation or an intra-frame operation on the basis of an output signal of the synthesizing circuit.

Video signal processing circuit and video signal processing method

The tone of video signals is corrected without degrading the tone of certain image features, such as a human face. A gain controller operates and outputs an adjustment value using a histogram output produced by a histogram generator. An average value of picture levels on a screen is detected by an average picture level detector. A histogram correction circuit calculates a look-up table, and a video signal correction circuit corrects the tone of the video signals using the look-up table.

Image quality correction circuit for video signals

A histogram generator creates a histogram to detect the characteristics of video signals. The histogram generator allows for a reduction in problems of instability caused by noise that may exist in other histogram generators. A width is allocated to thresholds used in creating the histogram, and signal values are counted after weighting those falling near a threshold.

Histogram generator

Aiming to improve color reproducibility of a red part having high color saturation, a gamma compensation apparatus of the present invention is composed of a bending point setting block,and a gamma compensation block,and bending point setting block,is composed of a high APL detection circuit,inputting an average picture level of an input luminance signal and for detecting and taking out a signal component higher than a designated level; a gain controller,for gain controlling the detected signal at the high APL picture detection circuit; and an adder,for adding a designated offset to the output of gain controller,, and gamma compensation block,is composed of a slice circuit,inputting a color difference signal (R-Y) and the output of bending point setting block,and taking out a color difference signal component higher than the output signal level of bending point setting block,; a gain controller,for adjusting the output level of slice circuit,; and a subtracter,for subtracting the output of gain controller,from the input color difference signal (R-Y) and outputting a gamma compensated color difference signal (R-Y)&prime;.

Gamma compensation apparatus

Red color saturation is increased and red color with higher purity can be reproduced by composing: a red color detection circuit 1 for detecting a red color signal having higher purity by inputting color differential signals (R-Y) and (B-Y) modulated by color subcarrier, subtracting the absolute value of the (B-Y) signal from the positive polarity component of the (R-Y) signal and removing the negative part of the subtracted signal; Y signal compensation block including: first gain controller 50b for controlling the output signal amplitude of red color detection circuit 1 and a subtracter 50a for subtracting the output signal of first gain controller 50b from a luminance signal Y; an (R-Y) signal compensation block including: second gain controller 51b for controlling the output signal amplitude of red color detection circuit 1 and an adder 51a for adding the output signal of second gain controller 51b and the input (R-Y) signal; and a (B-Y) signal compensation block including: third gain controller 52b for controlling the output signal amplitude of red color detection circuit 1, a polarity inverter 52c for inverting the output signal polarity of third gain controller 52b, a switch circuit 52d for selecting either input signal or output signal of polarity inverter 52c, a polarity discriminater 52e for discriminating the polarity of the input (B-Y) signal and controlling switch circuit 52d and an adder 52e for adding the output signal of switch circuit 52d and the input (B-Y) signal.

Pure red color detection circuit and color compensation circuit using

A histogram operating unit comprises: histogram generator which receives input video signals, and creates a histogram of input video signals, a first limiter for receiving a histogram generated by the histogram generator and an externally set first limit level, and restricting the frequency of the histogram created by the histogram generator to within a specified level, and outputting a restricted histogram, a first totaling circuit for calculating the number of samples of video signals produced by the first limiter, second totaling circuit for calculating the number of samples of the input video signals, a first subtractor for subtracting the output of the first totaling circuit from the output of the second totaling circuit, and a corrected histogram generator which receives the output of the first limiter and the output of the first subtractor, and creates the corrected histogram.

Histogram operating unit for video signals

A black level detecting circuit compares an input video signal with a current minimum value of input video signals, then detects a difference between the input signal and the current minimum value when the input value is smaller than the current minimum value, and then outputs the detected difference only during a detecting period of the black level, then corrects the minimum value by using this output for renewing the current minimum value, and finally outputs this renewed minimum value as a new minimum value of the input video signal. The black level detecting circuit also latches the minimum value during the vertical blanking pulse and initializes the minimum value during a vertical blanking period so as to detect a black level of the input signal. As such, the black level detecting circuit measures the black level only during a video period, thereby reducing detection errors due to noises, and also an automatic initialization of the minimum value during a blanking period can contribute to a more stable detection of the black level. The black level detected can be used effectively as a control signal over picture quality for each field or each frame.

Black level detecting circuit of video signal

A skin-color-area detector generates a skin-color-area signal from an input video signal. An average luminance level detector generates an average luminance level signal from a luminance signal. These signals are transmitted to a skin-color-corrector to generate skin-color-correction signals. At a saturation controller and at a luminance signal corrector which each receive the skin color corrections signals, skin-color is optimumly corrected. Thereby reproduction quality of skin-color signals in video signals is enhanced.

Reproduction circuit for skin color in video signals

An automatically adjustable black stretch control apparatus for a continually adjusting the black stretch of a luminance signal which comprises a black stretch control means for controlling the amount of stretch of the black part of the luminance signal. A luminance signal is input to a plurality of detecting means, each of which detects the percentage of the luminance signal that is within a specified range during a unit period (i.e. a frame). The output of each detecting means is input to one of a plurality of preprocessing means which generates a control index. The output of each preprocessing means is input to one of a plurality of inferring means for creating a synthesized function indicative of the quality of the signal from each of the detecting means. The black stretch control output determining means receives the output of each of the plurality of inferring means and determines the median value of the inferring means signals to determine the amount the black stretch of the luminance signal must be compensated in order to provide an optimum picture. Finally, the black stretch compensation amount control means controls the compensation amount of the black stretch control means according to the compensation amount calculated by the black stretch control output determining means.

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Takatsuki, Japan

Masahiro Takeshima