NLayer

NLayer is a fully managed, MIT-licensed MP3 to WAV decoder implemented in C# based on the MPEG specifications.

NLayer targets netstandard2.0 and net8.0, so it runs on .NET Framework 4.6.1+, .NET 8+, Unity, and Mono.

Usage

To use NLayer for decoding MP3, first reference NLayer.

using NLayer;

Then create an MpegFile, pass a file name or a stream to the constructor, and use ReadSamples for decoding the content:

// samples per second times channel count
const int samplesCount = 44100;
var fileName = "myMp3File.mp3";
var mpegFile = new MpegFile(filename);
float[] samples = new float[samplesCount];
int readCount = mpegFile.ReadSamples(samples, 0, samplesCount);

More information could be found in code documents.

Use with NAudio

NLayer is capable of using in conjunction with NAudio for file conversion and real-time playback.

You need to reference NAudio, NLayer and NLayer.NAudioSupport first.

using NAudio.Wave;
using NLayer.NAudioSupport;

Then create an Mp3FileReader, passing in a FrameDecompressorBuilder that uses the Mp3FrameDecompressor from NLayer.NAudioSupport:

var fileName = "myMp3File.mp3";
var builder = new Mp3FileReader.FrameDecompressorBuilder(wf => new Mp3FrameDecompressor(wf));
var reader = new Mp3FileReaderBase(fileName, builder);
// play or process the file, e.g.:
waveOut.Init(reader);
waveOut.Play();

NLayer.NAudioSupport currently targets NAudio 2. NAudio 3 support (which carries breaking Span<T> API changes) will follow once the NAudio 3 API stabilises.

Building

dotnet build NLayer.sln -c Release
dotnet test NLayer.sln -c Release

Every push and pull request is built and tested by the build GitHub Actions workflow.

Assemblies are strong-named with NLayerStrongNameKey.snk (checked into the repo root). Compiler warnings are treated as errors; the broader .NET code-analysis (CA) analyzers are not enabled — turning them on surfaces ~110 mostly-mechanical style/perf suggestions that can be addressed incrementally.

Releasing

Versioning is centralised in Directory.Build.props (<VersionPrefix>) and shared by both the NLayer and NLayer.NAudioSupport packages. Release notes live in RELEASE_NOTES.md. Packages are published to NuGet by the release workflow, which uses NuGet trusted publishing (OIDC) — no API key is stored in the repository.

• Pre-release: run the release workflow manually (Actions → release → Run workflow) from main. It publishes <VersionPrefix>-preview.<run>, or pass a milestone such as rc.1 for <VersionPrefix>-rc.1.
• Final release: bump <VersionPrefix>, rename the ### Unreleased heading in RELEASE_NOTES.md to ### <version> (DD MMM YYYY), commit, then push a matching v<version> tag (e.g. v2.0.0). The workflow packs, pushes to NuGet, and creates a GitHub Release.

See Docs/Releasing.md for the full step-by-step guide, trusted-publishing setup, and troubleshooting.