Flac

A macOS app for playing FLAC and other hi-res audio, built with SwiftUI. The whole point is bit-perfect playback — audio goes straight from the decoder to the output device with no resampling, no mixer graph, and nothing touching the signal unless you turn it on yourself.

What it does

Plays FLAC, ALAC (.m4a), PCM (.wav/.aiff), and DSD (.dsf, over DoP). Gapless between tracks that share the same sample rate, bit depth, and channel count.

For managing music there's folder scanning with live watched folders (FSEvents), M3U import/export, and an album view — a cover grid plus an Apple Music–style detail page with search.

The equalizer is a 6-band graphic EQ with 15 presets, and it's fully bypassable so it never gets in the way of bit-perfect output when you don't want it.

Two screens exist specifically for people who care whether their "hi-res" files are actually hi-res: Signal Path shows the real output format, bit-perfect status, and a live waveform pulled straight from the render callback, and Spectrogram runs a full-file FFT to flag files that were upsampled from something lossy. There's also on-demand FLAC integrity verification, checking a file's audio against the MD5 it has embedded in its own STREAMINFO block.

The now-playing bar has shuffle, repeat, its own independent digital volume, and output device switching, with Liquid Glass styling on macOS 26+.

Requirements

• macOS 14+
• Xcode / Swift 6
• flac from Homebrew (brew install flac) — needed for libFLAC via pkg-config

Building

swift build

swift build alone links against your Homebrew prefix's absolute paths, so it won't run as a standalone app. To get an actual .app bundle (bundles libFLAC/libogg and re-signs everything):

./Scripts/build-app.sh debug   # or: release
open .build/debug/FlacPlayer.app

Testing

swift test

Distribution

Scripts/notarize.sh does a release build, re-signs it with a Developer ID identity and hardened runtime, and submits it for notarization. Check the script's header for the one-time setup — you'll need a Developer ID certificate and stored notarytool credentials.

Project layout

• Sources/FlacPlayerCore — decoding, the bit-perfect output engine, the SwiftData library/playlist models, the EQ's DSP, and frequency analysis.
• Sources/FlacPlayer — the actual SwiftUI app: sidebar, the library/album/ playlist views, the now-playing bar, equalizer UI, and the player/inspector models.
• Sources/CFLAC — shim for the libFLAC system library.
• Tests/FlacPlayerCoreTests — unit tests, plus the audio fixtures they run against.