SBR, Parametric Coding及MPEG Surround解碼器中高品質低功率四相鏡射濾波器組之設計

Abstract

複數的四相鏡射濾波器組由於其無效果失真的特性已經被廣泛的用在SBR， Parametric Coding及Surround等MPEG-4音訊壓縮的標準裡。但是由於利用複數的四相鏡射濾波器組及後續在複數域中處理所產生的高複雜度負擔導致了採用實數的四相鏡射濾波器組為基本模組的低功率解碼器之發展。然而在實數的四相鏡射濾波器組產生的效果失真所導致的音訊缺陷是主要關心的議題。在此篇論文中採用實數的四相鏡射濾波器組所產生的音訊缺陷將被徹底地研究且提出一個全新的四相鏡射濾波器組之設計以達到高品質兼低功率的目的。而且此篇論文將會展示出將此種全新的四相鏡射濾波器組之設計應用在SBR， Parametric Coding及MPEG Surround解碼器中品質及複雜度上的優點

Due to the aliasing-free properties, the complex quadrature mirror filter (QMF) bank has been used in MPEG-4 audio standard on SBR, parametric, and surrounds coding. The high complexity overhead from the complex QMF bank and the complex data processing in the decoder leads to the development of low power decoder which adopts the real QMF bank as the basic building module to reduce the complexity. However the artifacts from the aliasing in the real QMF bank are the major concern. This paper studies the artifacts from the real QMF bank and proposes a novel QMF bank design to achieve both low complexity and high quality. Also, this paper applies the novel QMF bank to develop the high-quality and low-power SBR, parametric, and MPEG surround decoders and shows the merits in complexity and quality.