MPEG Surround (MPS) has been widely known as both efficient technique for encoding multi-channel audio signals and rich-features audio standard. However, the generation of residual signal in the basis of a single module in MPS encoder can be considered as not optimal to compensate for error due to down-mixing process. In this paper, an improved residual coding method is proposed in order to ensure the down-mixing error can be optimally minimised particularly for MPS operation at high bit-rates. The distortion introduced during MPS encoding and decoding processes is first studied which then motivates for developing an approach which is more accurate in determining residual signals for better compensation for the distortion. A subjective test demonstrates that the MPS with improved residual coding can be competitive to Advanced Audio Coding (AAC) multi-channel for encoding 5-channel audio signals at bit-rates of 256 and 320 kb/s.

This study presents a novel spatial audio coding (SAC) technique, called analysis by synthesis SAC (AbS‐SAC), with a capability of minimising signal distortion introduced during the encoding processes. The reverse one‐to‐two (R‐OTT), a module applied in the MPEG Surround to down‐mix two channels as a single channel, is first configured as a closed‐loop system. This closed‐loop module offers a capability to reduce the quantisation errors of the spatial parameters, leading to an improved quality of the synthesised audio signals. Moreover, a sub‐optimal AbS optimisation, based on the closed‐loop R‐OTT module, is proposed. This algorithm addresses a problem of practicality in implementing an optimal AbS optimisation while it is still capable of improving further the quality of the reconstructed audio signals. In terms of algorithm complexity, the proposed sub‐optimal algorithm provides scalability. The results of objective and subjective tests are presented. It is shown that significant improvement of the objective performance, when compared to the conventional open‐loop approach, is achieved. On the other hand, subjective test show that the proposed technique achieves higher subjective difference grade scores than the tested advanced audio coding multichannel.

Spatial hearing enables translation of an auditory scene into a perceived 3-D image by interpreting the acoustic cues related to the sounding objects, their locations, and the physical characteristics of the space. Spatial audio production requires multichannel audio signals in order to convey this information and increase the realism of a real or virtual environment for applications such as the home entertainment, virtual reality, and remote collaboration. As demand to spatial audio continues to expand, efficient coding of multichannel audio content becomes more and more important. This paper provides an overview of some well-known multichannel audio coding techniques and presents a new coding framework for improving the objective fidelity of the decoded signals. A closed-loop encoding system based on analysis-by-synthesis (AbS) principle applied on the MPEG surround (MPS) architecture is described. Comparison results are presented, which show that significant improvements can be achieved with a closed-loop system instead of the conventional open-loop system.