Time-varying MMSE modulated lapped transform and its applications to transform coding for speech and audio signals

作     者：Wang, GY Heute, U 

作者机构：Univ Kiel Inst Circuit & Syst Theory D-24143 Kiel Germany 

出 版 物：《SIGNAL PROCESSING》 (信号处理)

年 卷 期：2002年第82卷第9期

页      面：1283-1304页

核心收录：

学科分类：0808[工学-电气工程] 08[工学] 

主　　题：MODULATION (Electronics) TRANSFORMATIONS (Mathematics) CODING theory 

摘      要：The time-varying modulated lapped transform (MLT) is used in speech and audio coding schemes to adjust the time-frequency resolution, to eliminate pre-echoes in the reconstructed signal, and to improve the coding quality. In order to maintain the perfect-reconstruction property in transition periods, an asymmetrical window has to be used at cost of poorer frequency characteristics. We firstly generalize a window-design method for transition periods in the time-varying MLT with a rigorous proof of its PR property, then present a new window-design method, with which the prototype window is so designed that the total reconstruction distortion in presence of coefficient quantization is minimized. This leads to the time-varying minimum mean-square error (MMSE) MLT. Experiments have shown that the designed windows have better frequency characteristics than the sine window in both transition and regular periods. A general formulation of the quantization distortion for different quantization-error models and for all coding systems is given. A simplified optimal window-design algorithm without direct minimization of the distortion equation is suggested. As an example a transform-coding scheme with time-varying MMSE MLT for speech and audio signals is presented. (C) 2002 Elsevier Science B.V. All rights reserved.