US 6,052,156 AGranted

Digital color encoder having sampling frequency converter

AssigneeRicoh Company, Ltd.

InventorsTakuo Mukai, Kentarou Hara, Masaharu Adachi

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Abstract

A digital color encoder capable of reducing the aperture distortion of D/A conversion and the waveform distortion of the video signal without resulting in the increase of the consumed electric current. At first, digital signals sampled with a sampling frequency are inputted as original color signals. The digital composite color video signals of the sampling frequency fl are created from those signals by digital signal processing with the combination of matrix circuit, color burst controlling circuit, modulation circuit, addition circuit, and synchronization signal adding circuit, etc. Next, the sampling frequency of the composite color video signal is converted by a sampling frequency converting circuit inserted immediately before the D/A converter. The converted signal is further converted to an analog signal capable of being inputted into the TV set by a D/A converter, and the signal is outputted as a video signal.

Claims17

Dependent claims

A digital color encoder for executing a series of digital signal processings including a matrix operational calculation, a frequency band width limitation, a right angle two-phase balancing modulation, and a processing corresponding to an addition of a color burst signal and a synchronization signal, all respectively performed for original color signals obtained from digital video signals corresponding to three original colors of light, and thereby generating a digital composite color video signal sampled with a first sampling frequency, and further generating an analog composite color video signal to be inputted into a television image receiving set by converting the digital composite color video signal by use of a D/A converter, said digital color encoder comprising:

a sampling frequency converter for converting the digital composite color signal sampled with the first sampling frequency to a signal having a second sampling frequency higher than the first sampling frequency;
and
a filter having a passband around the higher second sampling frequency for receiving an output of the sampling frequency converter, wherein frequencies around the higher second sampling frequency output by the filter are thereafter input into the D/A converter,
wherein the conversion and filtering of the digital composite color video signal prior to the D/A conversion suppresses aperture distortion by the D/A conversion.

1 more element

A method of processing using a digital color encoder comprising steps of:

generating a digital composite color video signal sampled with a first sampling frequency;
converting the digital composite color video signal sampled with the first sampling frequency to a composite color video signal having a second sampling frequency higher than the first sampling frequency;
filtering the converted signal using a filter having a passband around the higher second sampling frequency, wherein frequencies around the higher second sampling frequency are output;
generating an analog composite color video signal from the digital composite color video signal having the second sampling frequency output by said filtering step,
wherein the conversion of the digital composite color video signal to the second sampling frequency prior and filtering to the D/A conversion suppresses aperture distortion by the D/A conversion.

2 more elements

Dependencies are inferred from the claim text.