Building a bit-perfect FLAC audio player using Flutter and Zig

[u/johnngugi]

Hey r/FlutterDev,

I wanted to share a project I’ve been working on called Listener (Link:https://github.com/johnngugi/listener).

It’s a custom bit-perfect audio player and streaming app. The goal was to send uncompressed FLAC PCM data directly to external DACs without the operating system interfering.

Most standard Flutter audio plugins route everything through the OS mixer, which inevitably resamples the audio. To get true bit-perfect playback, I needed to bypass the mixer entirely and talk directly to the native audio APIs (WASAPI on Windows, CoreAudio on macOS).

Here is how I set up the stack:

• The Audio Engine (Zig): Zig does all the heavy lifting. It decodes the FLAC files, manages a custom TCP network protocol for streaming, and pushes the audio buffers directly to the DAC using the native OS APIs.
• The Bridge (Dart FFI): Dart acts strictly as a control plane and never actually touches the audio buffers. Flutter simply sends commands (play, pause, seek, load) down to Zig via FFI. Keeping the buffers entirely within Zig ensures that Dart's garbage collection or UI thread overhead can never cause stutters in the audio stream.
• The Frontend (Flutter): The user interface is currently very barebones and needs a lot of work. The core focus so far has been getting the native audio pipeline rock solid.

I’m sharing this because bridging Flutter with a low-level systems language like Zig for high-performance audio isn't a super common use case, and I thought this control-plane architecture might be interesting to share.

I’d love any feedback on the FFI implementation or how I'm handling the native API integrations. Also, if anyone is passionate about audio UI and wants to critique (or help improve) the frontend, I'm all ears.