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Le codeur mpeg-2 AAC expliqué aux traiteurs de signaux

The mpeg-2 AAC coder explained to the signal processing experts

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Résumé

Descendant direct des codeurs audio mpeg- 1, dont le MP3 est la figure emblématique, le mpeg- 2 “Advanced Audio Coder” rassemble les techniques de compression les plus récentes et les plus ejficaces. D’une architecture classique, il est construit autour d’une transformée en cosinus discrète à résolution variable. En sortie de ce bane de filtres, l’opération de compression proprement dite consiste en une allocation dynamique de bits par sous- bandes fréquentielles, associeée à un module de codage entropique. L’allocation de bits est supervisée par un modèle psychoacoustique qui détermine le seuil d’audibilité des déformations subies par le signal dans le domaine fréquentiel. Cet article se veut un complément explicatif de la norme, mais aussi une introduction aux techniques de codage perceptuel de la musique.

Abstract

The MPEG- 2 Advanced Audio Coder is the latest issue of the MPEG audio encoders/decoders family, whose most popular version is known as MP3. It gathers many of the latest highly efficient sound compression techniques in a quite classically structured coder. The main part is based on a Discrete Cosine Transform with variable resolution. The output from this filterbank is compressed by the combination of an adaptive bit allocation module, according to frequency subbands, and a set of noiseless Huffman codebooks. Bit allocation is controlled by a psychoa-coustic model which determines an audibility threshold for signal distortion in the frequency domain. This article intends to explain the ISO standard without replacing it, and also to be a general introduction to perceptual audio coding.

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Correspondence to Olivier Derrien, Sonia Larbi, Marcos Perreau Guimares or Nicolas Moreau.

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Derrien, O., Larbi, S., Guimares, M.P. et al. Le codeur mpeg-2 AAC expliqué aux traiteurs de signaux. Ann. Télécommun. 55, 442–461 (2000). https://doi.org/10.1007/BF02995201

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  • DOI: https://doi.org/10.1007/BF02995201

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