Parallelizing Soft-Synths with Soft Real-Time Requirements

Though parallel processing of applications related to video processing and rendering are widespread, parallel processing of audio synthesis software (also known as soft-synths) is not much researched. This paper addresses our research and experiments in parallelizing digital audio synthesizers on a commodity multicore platform where these synthesizers are most commonly used. Soft real-time requirements and overheads of parallelization are two of the competing forces in this research. As a case study, the ALSA (Advanced Linux Sound Architecture) Modular audio Synthesizer (AMS) is evaluated. AMS employs a modular approach to digital music synthesis, is often part of a standard Linux installation package, has a GUI for user interactions, and like other audio synthesizers it has a soft real-time requirement. The main intentions of parallelization are for enhancing throughput and hence stability, whereby more complex and higher quality audio can be generated. The GUI based interactive approach adds an extra challenge of a dynamic call graph that can change on-the-fly. The paper compares the pros and cons of the different techniques adopt-ed, and highlights the advantages of parallelization. The lessons learnt can also be used in parallelizing other existing audio synthesizers and designing new parallel synthesizers from scratch.