BANDWIDTH EXTENSION METHOD AND APPARATUS FOR MODIFIED DISCRETE COSINE TRANSFORM AUDIO CODER

摘要

PROBLEM TO BE SOLVED: To provide a bandwidth extension method and apparatus applicable to MDCT-based speech/audio coders.SOLUTION: A method includes defining a transition band 103 for a signal 101 having a spectrum within a first frequency band, where the transition band is defined as a portion of the first frequency band 104, and is located near an adjacent frequency band 105 that is adjacent to the first frequency band 104. The present invention includes a signal processing logic for: analyzing the transition band 103 to obtain a transition band spectral envelope and a transition band excitation spectrum; estimating an adjacent frequency band spectral envelope; generating an adjacent frequency band excitation spectrum by periodic repetition of at least a part of the transition band excitation spectrum with a repetition period determined by a pitch frequency of the signal; and combining the adjacent frequency band spectral envelope and the adjacent frequency band excitation spectrum to obtain an adjacent frequency band signal spectrum.