FreeBSD audio diagnostics and optimization
This guide provides a comprehensive overview of audio diagnostics and optimization in FreeBSD, focusing on USB DAC devices and professional audio interfaces operating in bitperfect and real-time modes. It details key diagnostic tools like /dev/sndstat, hw.snd parameters, and sndctl(8), which offer insights into device states, buffer structures, and signal processing chains. The article emphasizes the importance of the xruns parameter as an indicator of audio stability, where non-zero values signal potential artifacts requiring configuration adjustments. It also covers system-level optimizations, including latency settings, USB polling rates, power management, and CPU C-states, all of which impact audio performance. Practical recommendations are provided for tuning these parameters to achieve stable, high-quality audio playback in professional and audiophile applications.