This paper discusses a new DSP based real-time implementation of the MPEG-2/4 AAC standards using a set of non-optimal solutions to reduce the computational load. These solutions comprise a novel implementation of a MDCT-based psychoacoustic model, managing a birth/death scheme which aims to overcome false power spectrum estimates due to the cosine transform, a smoothing of the scalefactors guided by an estimation of the increment in the quantization noise and a loop-free bit allocation method based on an overestimation of the noise level. These techniques provide both robustness and efficiency to the scheme. Other fixed-point DSP programming considerations required to achieve the real-time implementation, including a choice of a MDCT fast algorithm, are presented.

Authors: Duenas, Alberto; Perez, Rafael; Rivas, Begona; Alexandre, Enrique; Pena, Antonio
Affiliations: Prodys, Legan´es, Madrid, Spain ; E.T.S.E. Telecomunicaci´on. Universidade de Vigo, Vigo, Spain(See document for exact affiliation information.)
AES Convention: 112 (April 2002) Paper Number: 5556
Publication Date: April 1, 2002 Import into BibTeX
Subject: Low Bit-Rate Audio Coding
Permalink: https://www.aes.org/e-lib/browse.cfm?elib=11390

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