High Performance AUdio Computing

High-Performance Audio Computing (HiPAC) is a new domain of study that explores the potential for new advanced processor architectures to transform the current landscape of audio synthesis, processing and music composition.  Taking its name from the well-established domain of general High-Performance Computing (HPC), it considers the impact of  highly parallel floating-point  processors  which enable techniques previously disregarded as too computationally expensive to be performed faster than real-time.

"This is compute power far beyond what even the most starrry-eyed fortuneteller could have imagined! It will change the very nature of what audio is, and what audio engineers do, since it changes what is possible at a fundamental level."

(James Moorer, "Audio in the New Millennium", Journal of the Audio Engineering Society, May 2000)

HiPAC - key aspects.

At this early stage, we have identified a small number of aspects which we consider  distinguish HiPAC research from mainstream audio dsp research. Through collaboration and consultation with interested institutions, individuals and industrial developers, we hope and expect to refine and probably expand this list.
  1.  the research and development of compute-intensive tools for audio and music processing
  2.  a focus on the  use of massively-parallel and mesh CPU technology
  3.  the use of "no-compromise" or "ideal" algorithms, rather than of techniques that may be efficient but at the loss of generality.
  4.  sonic and artistic  value takes precedence over issues of computational load (since we are presuming that that load can be met by next-generation technology).
Some possible HiPAC programmes:

  •  rather than implement standard digital wavguides on Teraflop hardware, develop uncompromised physical models of strings, plates etc by means of finite difference meshes.
  •  generate real-time reverb by direct modelling of the physical space (over the full frequency range of interest), rather than by means of sampled impulse responses or delay networks.
  • investigate the optimum  processor architectures for audio in terms of parallelism, synchronous v threaded computation, latency, and use of large shared memory spaces. How can we most efficiently combine inherently recursive processes such as filters with block-based algorithms suited to implementation on massively-parallel hardware?
  • what progamming languages do we need to support HiPAC research?
  • < your project here!>

HiPAC at Bath University

This subject is as new for us as it will be for anyone else. So far, we have one project to report, and one collaboration.

The Sliding Phase Vocoder and TFM.

This project, funded by the AHRC, ran for a year from September 1 2006.  The project aimed to develop the Sliding DFT (SDFT), where the analysis frame is updated every sample, into a full Phase Vocoder. Using this we have developed Transformational FM (TFM), pitch shifting of an input sound where the pitch can be modulated at audio rates, sample by sample, thus applying the familiar Chowning FM behaviour to an arbitrary input sound. With the SPV we have found that compared to the standard phase vocoder (pvoc), latency is reduced by up to 75%. It is of course much slower than conventional pvoc - but the use of HiPAC-grade hardware will enable it to run in real time, with tantalising possibilities for interactive live performance.

The results were presented at ICMC 2007 (Copenhagen). The slides from this presentation, together with some audio examples, are available here.

Collaboration with Clearspeed Technology PLC

Clearspeed manufactures double-precision floating-point accelerator chips (together with PCI-X and PCI-e cards), widely used to accelerate supercomputer clusters. A key feature of this hardware is very low power consumption. Several cards can comfortably be fitted within one host PC. Each card uses two Clearspeed CSX600 chips, offering computation up to 55Gflops. They implement a SIMD computational model, with 96 double-precision Processing Elements (PEs) running in parallel, per chip. The NOS-DREAM studio currently has four cards, running in pairs under Linux and Windows XP. We are investigating the use of this hardware to accelerate HiPAC processes such as the SPV to real-time capability.

For more information please contact us.