Implementation of an object audio system based on MPEG-4 audio lossless coding on DSP

In this paper, we propose an object audio system on digital signal processor (DSP) that consists of MPEG-4 audio lossless coding (ALS) to provide high-quality audio. The complexity reduction in the designed object audio system is very critical issue because the system requires several MPEG-4 ALS decoders, as many as the number of objects. A method to efficiently use internal memory on DSP is suggested to overcome the high-complexity situation that happens with the use of external memory. A low-complexity finite impulse response (FIR) filter is also proposed because the short-term prediction filter in the MPEG-4 ALS decoder has the highest complexity in MPEG-4 ALS decoder blocks. A method for efficient use of internal memory is designed so that the critical data of MPEG-4 ALS decoders use internal memory as much as the size of the data for a decoder, and the internal memory is shared with the MPEG-4 ALS decoders. The proposed FIR filter reduces the complexity of the short-term prediction filter by 25% compared to direct convolution. A proposed method for an object audio system is evaluated on DSP; it consists of 12 objects. The proposed audio system has a reduction of complexity by 83% with the application of the two proposed methods, and the audio system operates in real time on DSP. This means that high-quality object audio can be serviced for multimedia products.

I. Introduction

An object audio coding that independently processes audio objects has been receiving the increasing interest in users' audio systems and intelligent multimedia. Desired object can be controlled by users in music, news and other multi-media service. Users are authorized to design the listening sound of multimedia service. Currently, spatial audio object coding (SAOC), which is based on audio down-mixing technology, has been standardizing in moving picture experts group (MPEG) [1]. SAOC has a high compression ratio due to the audio down-mixing technology, but an up-mixed object receives a little interference from other objects. The object that is selected to turn off at an object audio system cannot be perfectly removed in music by the interference.