DRA Audio Coding Standard: An Overview

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20.1 Introduction

A lossy audio coding or compression algorithm explores statistical redundancy and perceptual irrelevance of an input audio signal, which may include multiple channels, to obtain a compact representation suitable for efficient transmission or storage. Figure 20.1 is a generic architecture designed to achieve this and is the basis for most audio coding algorithms or standards. The following is a brief description of its major components:

  • Time-Frequency Analysis: Frequently referred to as an analysis filter bank, it transforms each channel of the input audio signal into a set of time-frequency parameters suitable for quantization and encoding so that their statistical redundancy and perceptual irrelevance can be readily exploited. It may come in the form of Fourier transform, discrete cosine transform(DCT), linear prediction, or subband filter banks. Modified discrete cosine transform (MDCT) is a filter bank widely used in audio coding standards.