Nec Corporation

Hidemitsu Nikoh

Hiroshi Morito

Munenori Kobayashi

A PAL encoder comprises phase converter, first and second low-pass filters, a burst signal adder, a chrominance subcarrier generator, and a modulator. The phase converter converts digital first and second color-difference signals into digital U-axis and V-axis signals. The first and second low-pass filters pass low-frequency components of the digital U-axis and V-axis signals to produce band-rejected U-axis and V-axis signals, respectively. The burst signal adder adds a predetermined burst signal to the band-rejected U-axis and V-axis signals to produce burst-added U-axis and V-axis signals, respectively. The chrominance subcarrier generator outputs digital sine and cosine signals of the chrominance subcarrier. The modulator multiplies the burst-added U-axis signal by the sine signal and the burst-added V-axis signal by the cosine signal and adds the multiplied results to produce a digital chroma signal.

Pal encoder using a digital signal processing

A color-signal enhancing circuit of the invention comprises a pair of first and second high-pass filters, a control circuit, and a pair of first and second gain controllers. The high-pass filters provide a predetermined frequency region restriction to color difference signals. The control circuit may comprise a first and second gain controllable amplifiers which provide a predetetermined coefficient to outputs from the high-pass filters, an adder which adds outputs from the first and second amplifiers, and a convertor which provides to an output of the adder a coefficient calculated in a predetermined operation in accordance with the polarity of input signals inputted thereto. In an alternative arrangement, a pair of the high-pass filters may be replaced by a pair of low-pass filters. The gain control signal is obtained from the information on high frequency components or on low frequency components of color difference signals and, with this single gain control signal, the gains of the color difference signals inputted are controlled, whereby it is possible to enhance color signals in such a way that there will be no appearance of false colors at turning points of color changing.

Color signal enhancing cirucit for improving the resolution of picture

An output apparatus for image signals includes an image signal processing circuit for providing a digital luminance signal, a digital color signal, a digital composite video signal etc., a multiplexing circuit for multiplexing these signals to be positioned alternately on a time axis, a D/A converter for converting the digital multiplexed signal to an analog multiplexed signal, and plural signal holding circuits for an analog luminance signal, an analog color signal, an analog composite video signal etc. separated from the analog multiplexed signal, respectively. Therefore, only one D/A converter is used therein, so that the cost is decreased and the size becomes small.

Output apparatus for image signals

In a digital video signal compensation circuit, a high frequency component of a digital video signal is obtained in a high-pass filter, and the high frequency component is compared in a comparator with a threshold signal, thereby determining whether the high frequency component is an edge component or a noise component. Where the high frequency component is the edge component, the high frequency component is added in an adder to the digital video signal, and where the high frequency component is a noise component, the high frequency component is subtracted in the adder from the digital video signal in accordance with the sign conversion of the high frequency component. Therefore, only one adder is provided in the digital video signal compensation circuit. That is, it is not necessary that an adder and a subtracter are provided therein.

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Tokyo, Japan

Hidemitsu Nikoh