Digital-to-analog conversion multiple-format video encoder
AssigneeRohm Co., Ltd.
InventorYasunori Kawamura
Life of this patent
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Abstract
A multiple-format video encoder stores values of the sine and cosine functions in a ROM. According to the externally specified video format, an address calculating circuit calculates the addresses at which to access the ROM. In the multiple-format video encoder, a luminance/color-difference signal generating circuit generates color-difference signals B-Y and R-Y from digital RGB signals. A first multiplying circuit multiplies the color-difference signal B-Y by the values of the sine function stored in the ROM at the addresses specified by the address calculating circuit and multiplies the color-difference signal R-Y by the values of the cosine function stored at the same addresses.
Claims13
A multiple-format video encoder comprising:
- a luminance/color-difference signal generating circuit that receives digital RGB signals to be inputted in synchronism with clock pulses at a predetermined frequency and generates a luminance signal and a color-difference signal from the RGB signals;
- a memory that stores trigonometric function values covering a predetermined number of phases at each address thereof for each of the phases and outputs a trigonometric function value stored at a designated address;
- and
- an address calculating circuit that receives a setting signal for selecting a predetermined video format from among a plurality of video formats each having a different chrominance subcarrier frequency, the address calculating circuit calculates a value to be added based on the chrominance subcarrier frequency of the predetermined video format selected with the setting signal, the predetermined number of phases, and the predetermined frequency of the clock pulses, and the address calculating circuit designates a next address of the memory by adding the calculated value to be added to the designated address,
- wherein a composite color video signal of the predetermined video format selected with the setting signal is generated based on the color-difference signal, the luminance signal, and a trigonometric function value stored in an address designated by the address calculating circuit.
A multiple-format video encoder comprising:
- a luminance/color-difference signal generating circuit that receives digital RGB signals to be inputted in synchronism with clock pulses at a predetermined frequency, generates a luminance signal and a color-difference signal from the RGB signals, and feeds out the luminance and the color-difference signals;
- a memory that stores trigonometric function values covering a predetermined number of phases at each address thereof for each of the phases and outputs a trigonometric function value stored at a designated address;
- and
- an address calculating circuit that receives a setting signal for selecting a predetermined video format from among a plurality of video formats, comprising:
- a value selecting circuit that divides a value resulting from multiplying the chrominance subcarrier frequency of the predetermined video format by the predetermined number of phases by the predetermined frequency of the clock pulses and outputs a result as a value to be added;
- an adder that adds the value to be added to the designated address and outputs a value to be used for deciding an address to be designated;
- a flip-flop circuit that temporarily stores the value output from the adder and feeds out this value in synchronism with regular clock pulses as the address to be designated;
- a multiplying circuit for multiplying the color-difference signal by a trigonometric function value read from the designated address and outputting a value therefrom, and
- an adder for adding the value output from the multiplying circuit to the luminance signal to generate and output a composite color video signal.
Dependencies are inferred from the claim text.