A virtual DSP architecture for audio applications from a complexity analysis of MPEG-4 structured audio

The MPEG-4 audio standard provides several toolsets for natural and synthetic sound coding. Among them, the most innovative in terms of multimedia applications is Structured Audio (SA), which implements a high level, structured description of sound instead of the usual compression techniques based on psychoacoustics and subband analysis. SA permits to encode synthesis and processing algorithms by its Structured Audio Orchestra Language (SAOL), and it can theoretically be used to specify any other audio decoder. This great flexibility introduces a challenging implementation problem, which in a normative framework has to be solved by a systematic approach. In the first part of the paper, it is described how the SA decoding process can be analyzed in a platform independent way in order to determine the fundamental figures of this coding technique; it is then shown how the proposed method is being used for the MPEG-4 SA conformance test. In the second part the design of a virtual digital signal processor (DSP) architecture is presented, based on the results of the complexity analysis. This architecture is able to exploit the intrinsic data level parallelism of many Audio algorithms and to consistently reduce the implementation cost. Experimental results prove the effectiveness of the approach and its suitability for implementations on modern superscalar DSPs and multimedia processors.