Parallel Wave Digital Filter Implementations of Audio Circuits with Multiple Nonlinearities

Modern audio systems and musical effects feature multicore processing units. Thus, the development of parallel audio processing algorithms capable of exploiting the architecture of such hardware is in order. In this paper, a parallel version of the hierarchical scattering iterative method (HSIM), a technique based on wave digital filter principles recently proposed for the emulation of multiphysics audio circuits containing multiple nonlinear one-ports and nonlinear transformers, is presented. HSIM operates in a modular fashion, and it is characterized by a high number of embarrassingly parallelizable operations, making it a good candidate for parallel execution. After analyzing HSIM from the parallel computing perspective, three different strategies for the distribution of HSIM workload among threads of execution are proposed, showing how to compute the maximum achievable speedup. The emulation of a possible output stage of a vacuum-tube guitar amplifier is considered, and a performance comparison between parallel and serial implementations of HSIM is presented, pointing out a speedup of nearly 30%. The proposed method thus proves to be promising for virtual analog modeling applications, leading the way towards the parallel digital emulation of increasingly complex audio circuits.