METHOD AND DEVICE FOR ORTHOGONAL TRANSFORMATION OPERATION AND INVERSE ORTHOGONAL TRANSFORMATION OPERATION AND DIGITAL SIGNAL ENCODING AND/OR DECODING DEVICE

摘要

PURPOSE: To prevent overflow on the way of operation and to omit the unnecessary scale down operation, which causes degradation of the operation precision so as to reduce the noise due to operation error. ;CONSTITUTION: In the digital signal decoding device which subjects the encoded output of a digital signal encoding device, which analyzes the frequency of an input digital signal by orthogonal transformation and quantizes and encodes the analysis output and records or transmits it, to frequency synthesis in IMDCT circuits 223 to 225 by inverse orthogonal transformation (IMDCT) to convert it from the frequency base to the time base at the time of reproducing or receiving and decodes this encoded output converted to the time base, an input data string of each calculation formula is compared with a preliminarily set scale down discrimination reference value to adaptively perform the scale down operation in the operation process of IMDCT in IMDCT circuits 223 to 225.;COPYRIGHT: (C)1994,JPO&Japio