Patent ID: 6185595
Filing Date: 2001-02-06
Classification: G06F

Abstract:
A discrete cosine transformation operation circuit comprising:an input data holding circuit which holds input data from outside in synchronization with a first timing signal having a first frequency;a coefficient storage unit storing predetermined transformation coefficients;a multiplier which multiplies a transformation coefficient from said coefficient storage unit and an input data from said input data holding circuit in synchronization with a second timing signal having a second frequency which is substantially four times as high as the first frequency;a cumulative adder which executes cumulative adding operations for the multiplication results sequentially outputted from said multiplier and sequentially provides cumulative adding results; andan output circuit which operates in synchronization with a third timing signal having a third frequency lower than the second frequency and which includes operation circuits executing predetermined operations between the cumulative adding results sequentially outputted from said cumulative adder, to output a discrete cosine transformation operation result,wherein the predetermined transformation coefficients are DCT transformation coefficients,and wherein the output circuit includes an adder which executes an adding operation between the cumulative adding results;a subtracter which executes a subtracting operation between the cumulative adding results;a plurality of registers each of which holds one of an output from the adder and an output from the subtracter; anda multiplexer for selecting one of the outputs of said registers,wherein a discrete cosine transformation operation result is provided from said adder by adding a first cumulative adding result with a second cumulative adding result in the cumulative adding results, the other discrete cosine transformation operation result is provided from said subtracter by subtracting the first cumulative adding result with the second cumulative adding, the provided discrete cosine transformation operation results are stored in the registers and one of the discrete cosine transformation operation results held in the registers is outputted from the multiplexer.