Low-Latency Music Software Using Off-The-Shelf Operating Systems

Operating systems are often the limiting factor in creating low-latency interactive computer music systems. Real-time music applications require operating system support for memory management, process scheduling, media I/O, and general development, including debugging. We present performance measurements for some current operating systems, including NT4, Windows95, and Irix 6.4. While Irix was found to give rather good real-time performance, NT4 and Windows95 suffer from both process scheduling delays and high audio output latency. The addition of WDM Streaming to NT and Windows offers some promise of lower latency, but WDM Streaming may actually make performance worse by circumventing priority-based scheduling.