Perceptual coding of audio signals using separated irrelevancy reduction and redundancy reduction

US7110953B1 · kind B1 · utility

Assignee

• Agere Systems Inc. · US

Inventors

• Bernd Edler · Hannover, DE
• Gerald Schuller · Erfurt, DE

Key dates

• Filing date: Jun 2, 2000
• Grant date: Sep 19, 2006
• Expiry date: Dec 10, 2022

Classification

• Technology area (CPC G): Physics
• CPC primary: G10L19/02
• WIPO field: Computer technology
• WIPO sector: Electrical engineering

Abstract

A perceptual audio coder is disclosed for encoding audio signals, such as speech or music, with different spectral and temporal resolutions for redundancy reduction and irrelevancy reduction. The disclosed perceptual audio coder separates the psychoacoustic model (irrelevancy reduction) from the redundancy reduction, to the extent possible. The audio signal is initially spectrally shaped using a prefilter controlled by a psychoacoustic model. The prefilter output samples are thereafter quantized and coded to minimize the mean square error (MSE) across the spectrum. The disclosed perceptual audio coder can use fixed quantizer step-sizes, since spectral shaping is performed by the pre-filter prior to quantization and coding. The disclosed pre-filter and post-filter support the appropriate frequency dependent temporal and spectral resolution for irrelevancy reduction. A filter structure based on a frequency-warping technique is used that allows filter design based on a non-linear frequency scale. The characteristics of the pre-filter may be adapted to the masked thresholds (as generated by the psychoacoustic model), using techniques known from speech coding, where linear-predictive co…