Very low bit rate parametric audio coding

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Advances In Parametric Audio Coding

Parametric modelling provides an efficient representation of general audio signals and is utilised in very low bit rate audio coding. It is based on the decomposition of an audio signal into components which are described by appropriate source models and represented by model parameters. Perception models are utilised in signal decomposition and model parameter coding. This paper gives a brief tutorial overview of parametric audio coding and describes the parametric coder currently developed in the MPEG-4 Audio standardisation. Recent advances as well as novel approaches in this field are presented. 1. INTRODUCTION From a physical point of view, the obvious representation of an audio signal x is its temporal sound pressure function (waveform) x(t). On the other hand for example, the score of a piece of music provides a rather abstract representation of an audio signal. Although there are many ways to transform a score into an audio signal, this ambiguity is acceptable for many applica..

An Overview Of Mpeg-4 Audio Version 2

this paper, first a brief overview of the MPEG-4 Audio Standard and the audio tools available in Version 1 is given. Then the audio tools added in Version 2 are introduced. These tools are described in more detail and their status in the ongoing standardisation process is discussed. Finally an outlook on future developments is presented and conclusions are drawn

Concepts for Hybrid Audio Coding Schemes Based on Parametric Techniques

Recently an audio coding technique based on a signal representation by parameters describing harmonic tones, individual sinusoidal components and noise components has been presented, which shows its highest efficiency at very low bit rates. In this paper concepts for combination with other techniques for extending the applicability at higher bit rates and for improving the quality in the presence of speech are presented. 1 Introduction A recently presented object based analysis/synthesis audio coder for very low bit rates is based on a signal representation which describes different components of an audio signal by appropriate parameter sets [1]. Together with transform coding and speech coding techniques it has been integrated in the MPEG-4 Audio development [2]. For harmonic tones the most important parameters are the fundamental frequency and the amplitudes of the partials. Individual sinusoidal components are represented by their frequencies and amplitudes, while noise components ..