Improvement of the perceptual quality of the sbr (spectrally band replication) and hfr (high frequencies - reconstruction) coding method by means of an adaptive adding background noise and limitation of the noise substitution

摘要

The present invention provides a new method and an apparatus for spectral envelope encoding. The invention teaches how to perform and signal compactly a time/frequency mapping of the envelope representation, and further, encode the spectral envelope data efficiently using adaptive time/frequency directional coding. The method is applicable to both natural audio coding and speech coding systems and is especially suited for coders using SBR [WO 98/57436] or other high frequency reconstruction methods.