Enhancing perceptual quality of sbr (spectral band replication) and hfr (high frequency reconstruction) coding methods by adaptive noise-floor addition and noise substitution limiting

摘要

The present proposes methods and an apparatus for enhancement of audio source coding systems utilising high frequency reconstruction (HFR). It addresses the problem of insufficient noise contents in a reconstructed highband, by Adaptive Noise-floor Addition. It also introduces new methods for enhanced performance by means of limiting unwanted noise, interpolation and smoothing of envelope adjustment amplification factors. The present invention is applicable to both speech coding and natural audio coding systems.