SoundPrivate Reference

Shipped

Professional audio analysis tool with EBU R128 loudness metering, spectrum, stereo field, and dynamics. Available as a macOS app and AU plugin.

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SoundPrivate Reference screenshot 1

Overview

SoundPrivate Reference is a dual-component audio analysis tool: a standalone macOS desktop app for batch offline analysis and a real-time Audio Unit plugin for in-DAW metering. It provides EBU R128 loudness measurement, frequency spectrum analysis, stereo field visualization, dynamics metering, BPM/key detection, and CSV export — built for mixing, mastering, and research workflows.

Tech Stack

Language: Swift (pure Swift + C interop for libebur128)UI: SwiftUIAudio: AVFoundation, AVAudioEngine, Accelerate/vDSP (FFT, filtering, peak detection)Loudness: libebur128 C library (EBU R128 standard)Build: Swift Package Manager (desktop) + Xcode (AU extension)Platform: macOS 14+Testing: Swift Testing framework

Engineering Highlights

  1. 01libebur128 C integration — Embedded the reference C implementation of EBU R128 loudness standard directly in Swift via C interop. Cross-validated against FFmpeg's ebur128 filter with deterministic test fixtures.
  2. 0212x batch processing speedup — Swift TaskGroup with CPU-core concurrency for parallel analysis. Optimized for stem separation research (340 files in 14 minutes on M4 Max).
  3. 03Dual architecture — Offline (desktop, libebur128 + FFmpeg backend) and real-time (AU plugin, Accelerate/vDSP) implementations validated against same reference. Different DSP paths for different use cases.
  4. 04App Group sync — Desktop and plugin share analysis profiles via macOS App Group shared storage. Profiles created in desktop appear in plugin in real-time.
  5. 05K-weighting filter — Custom DSP implementation of ITU-R BS.1770-4 perceptual weighting curve for real-time loudness metering.

Stats

67 Swift source files + 1 C library
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12 commits over 6 months
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40+ analysis metrics
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20+ CSV export fields per track
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