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Convention Paper

An Improved Distortion Measure for Audio Coding and a Corresponding Two-Layered Trellis Approach for Its Optimization

Authors: Melkote, Vinay; Rose, Kenneth

AES Convention 125 · Paper 7505 · October 2008

Abstract

The efficacy of rate-distortion optimization in audio coding is constrained by the quality of the distortion measure. The proposed approach is motivated by the observation that the Noise-to-Mask Ratio (NMR) measure, as it is widely used, is only well adapted to evaluate relative distortion of audio bands of equal width on the Bark scale. We propose a modification of the distortion measure to explicitly account for Bark bandwidth differences across audio coding bands. Substantial subjective gains are observed when this modification over plain NMR is used in the Two Loop Search, for quantization and coding parameters of scalefactor bands in an AAC encoder. Comprehensive optimization of the new measure, over the entire audio file, is then performed using a two-layered trellis approach, and yields nearly artifact-free audio even at low bit-rates.

Details

Published in
AES Convention 125
AES Convention
125
Paper number
7505
Publication date
October 6, 2008
Session subject
Audio Coding
Affiliation
Dept. of Electrical and Computer Engg., University of California Santa Barbara (See document for exact affiliation information.)
Type
Convention Paper