分頻式正弦波激勵音訊編碼之研究

Abstract

在本論文中, 我們使用分頻與以多重正弦波為激勵源的線性預估編 碼器, 配合以聽覺遮敝效應為基礎的位元配置, 達到64kb/s高品質之音訊 編碼. Most current work in LPC-based audio coders employ either multipulse orcodebook to represent the excitation. But their near white spectra can not precisely describe the pulselike characteristics of residual spectra. In thisthesis, we explore the benefits of the combined use of band-splitting and sinusoidal excitation representation in the design of analysis- by-synthesispredictive audio coders. One enhancement that further increases performanceis the use of a novel bit allocation scheme, in which bit quota is dynamicallyallocated according to the preceptually derived masking threshold. Informal listening tests shows that the combined use og multi- sinusoid excitation modeland band-splitting sllows the implementation of an LPC-based audio coder thatdelivers high quality audio reproduction at the rate of 64 kb/s.