Patent ID: 7076471
Filing Date: 2006-07-11
Classification: G06F

Abstract:
1. A computer implemented filtering method for use in decoding a digital signal from a frequency domain to a time domain, comprising: inputting a digital signal; a first step of multiplying an input data stream and a transformation matrix that is decomposed into a sparse matrix from an inverse MDCT transformation matrix for making the inverse MDCT transformation of said input data stream composed of a plurality of data blocks, and has a smaller size than said inverse MDCT transformation matrix, to acquire an output data stream composed of a plurality of data blocks; a second step of storing predetermined data contained in each data block of the output data stream; and a third step of generating a digital signal in the time domain on the basis of each data block generated in the first step and the predetermined data stored in the second step in processing the data block in the first step, and outputting the digital signal in the time domain generated in the third step, wherein the third step includes determining side information including information regarding decoding of the data block, and switching a processing method used for generating the digital signal in the time domain on the basis of the side information; the first step includes a fourth step of making a DCT (Discrete Cosine Transform)-IV transformation process for each data block of the input data stream; the second step includes a fifth step of storing a part of a process result of each data block at the fourth step that is used in processing the data block at the fourth step, and the third step further comprises: a sixth step of folding back and expanding a part of the process result of each data block in the fourth step other than the part of the process result stored in the fifth step and multiplying the expanded data by a predetermined window to generate a first process result, and folding back and expanding a part of the data block that is stored in the fifth step and multiplying the expanded data by a predetermined window to acquire a second process result, and a seventh step of adding the first and second process results acquired in the sixth step.