AudioLens

A native macOS audio player for musicians, built with Swift + AppKit.

Status: Early scaffolding. The architecture is in place; DSP wiring is in progress.

Feature Goals

1. Multi-format playback — anything the OS can't decode natively (Opus, WavPack, Musepack, …) via SFBAudioEngine.
2. Waveform visualization — Metal-rendered, with on-disk overview cache.
3. Section selection + looping — one or more regions, scheduled through AVAudioPlayerNode.
4. High-quality pitch shifting & time stretching — Rubber Band Library (R3 "finer" engine) wrapped in a custom AUAudioUnit. Cent-by-cent and semitone-by-semitone pitch, large stretch factors.
5. Graphic equalizer — multi-band, built on AVAudioUnitEQ.

Architecture

File → SFBAudioEngine decoder → AVAudioPCMBuffer
                                        ↓
AVAudioPlayerNode → RubberBandAU → AVAudioUnitEQ → MainMixer → Output
                         ↓
                    Tap → Waveform / level meters

Stereo only. Real-time and offline pitch/time changes both supported (RT for live control, offline for highest-quality renders).

Requirements

• macOS 26 (Tahoe) or later
• Xcode 17+
• Swift 6

Building

open AudioLens.xcodeproj

If the .xcodeproj ever drifts from project.yml, regenerate it with XcodeGen:

brew install xcodegen
xcodegen generate

Dependencies

SFBAudioEngine (required)

Multi-format audio decoding (Opus, FLAC, Vorbis, WavPack, Musepack, Monkey's Audio, Shorten, True Audio, plus everything Core Audio handles natively). Add it through Xcode the first time you build:

1. With AudioLens.xcodeproj open in Xcode: File → Add Package Dependencies…
2. Enter the URL https://github.com/sbooth/SFBAudioEngine
3. Dependency Rule: Up to Next Major Version from the version Xcode pre-fills (currently 0.12.x)
4. Add the SFBAudioEngine product to the AudioLens target

Once added, import SFBAudioEngine in Audio/SFBAudioLoader.swift resolves and the project builds.

Rubber Band Library (required for high-quality pitch / time)

Rubber Band Library provides the R3 "Finer" engine for pitch shifting and time stretching. GPL-2.0-or-later (compatible with this project's GPL-3.0). The source is vendored as a git submodule and compiled in-tree by Packages/RubberBand — no Homebrew or other system install needed, and the resulting .app is fully self-contained.

Setup (one-time, after cloning):

git submodule update --init --recursive

Then in Xcode: File → Add Package Dependencies… → Add Local…, navigate to Packages/RubberBand in this repo, and add the CRubberBand product to the AudioLens target.

Audio/RubberBandStretcher.swift imports the C API via #if canImport(CRubberBand), so the project still builds before the package is added — the Rubber Band wrapper just isn't compiled in until then.

License

GPL-3.0-or-later. See LICENSE.