CodeBrix.Audio.Opus.BsdLicenseForever 1.0.212.830

CodeBrix.Audio.Opus

Fully managed Ogg Opus decoding and encoding for CodeBrix.Audio, with no native binaries on any platform. CodeBrix.Audio.Opus depends only on .NET and CodeBrix.Audio, and is provided as a .NET 10 library and associated CodeBrix.Audio.Opus.BsdLicenseForever NuGet package.

CodeBrix.Audio.Opus supports applications and assemblies that target Microsoft .NET version 10.0 and later. Microsoft .NET version 10.0 is a Long-Term Supported (LTS) version of .NET, and was released on Nov 11, 2025; and will be actively supported by Microsoft until Nov 14, 2028. Please update your C#/.NET code and projects to the latest LTS version of Microsoft .NET.

Why this is a separate package

CodeBrix.Audio holds a deliberate licence bar of MIT or more permissive, which is what its CodeBrix.Audio.MitLicenseForever package id promises. Opus cannot meet it: every managed Opus implementation is a port of libopus, and libopus is BSD-3-Clause. So Opus support ships here instead, under BSD-3-Clause, as an add-on. Add this package and CodeBrix.Audio's promise is unchanged; skip it and nothing about CodeBrix.Audio changes either.

One call turns it on

using CodeBrix.Audio.Opus;

CodeBrixAudioOpus.Register();   // once, at application start-up

After that, .opus files play through AudioFilePlayer, SoundEffectClip, WaveOutEvent, the CodeBrix.Platform AudioPlayer add-in and the CodeBrix.Platform GameEngine, open by file name through AudioFileReader, and can be recorded by the engine's Recorder — none of which needs any other change. The application takes the dependency and makes the call; the add-ins never do.

There is deliberately no module initializer doing this for you: a module initializer only runs once something in the assembly is touched, which trimming and lazy assembly loading make unreliable, so the package would work in a debug build and silently fail in a trimmed publish.

CodeBrix.Audio.Opus supports:

• Decoding and playing Ogg Opus (.opus) — voice notes, podcasts, yt-dlp output, Wikimedia audio
• Encoding to Ogg Opus, from any input sample rate
• Recording straight to .opus through the CodeBrix.Audio engine's Recorder
• Exact seeking, and durations that account for the encoder's pre-skip
• Reading and writing Opus tags (TITLE, ARTIST, and the rest)
• Mono and stereo — Opus channel mapping family 0, which covers ordinary Opus files
• Every platform CodeBrix.Audio runs on, including linux-riscv64: there is no native code here

Sample Code

Play a .opus file

using CodeBrix.Audio.Opus;
using CodeBrix.Audio.Playback;

CodeBrixAudioOpus.Register();          // once, at start-up

var media = new AudioFilePlayer();
media.Load("voice-note.opus");         // Duration is available as soon as Load returns
media.Play();

Read a .opus file as float samples

using CodeBrix.Audio.Opus;

using var reader = new OpusFileReader("music.opus");
// reader.WaveFormat is 48 kHz 32-bit IEEE float - Opus decodes at 48 kHz, always.
// reader.EncoderInputSampleRate is what the ENCODER was given (often 16000 for a voice
// note); it is informational and never used to convert anything.

var buffer = new byte[reader.WaveFormat.AverageBytesPerSecond];
int read;
while ((read = reader.Read(buffer, 0, buffer.Length)) > 0)
{
    // interleaved 32-bit floats in [-1, 1]
}

Write a .opus file

using CodeBrix.Audio.Opus;

var options = new OpusFileWriterOptions
{
    Bitrate = 32_000,
    Profile = OpusEncodingProfile.Voice   // Music is the default
};
options.Tags["TITLE"] = "Voice memo";

using (var writer = new OpusFileWriter("memo.opus", sampleRate: 44100, channels: 1, options))
{
    writer.Write(samples);   // any input rate; resampled to 48 kHz on the way in
}
// Dispose is what finishes the file - see the note below.

Record straight to .opus

CodeBrixAudioOpus.Register();

using var stream = File.Create("recording.opus");
var recorder = new Recorder(captureDevice, stream, "opus");
recorder.StartRecording();

Sharp edges

• Dispose the writer. Like WaveFileWriter, OpusFileWriter only produces a complete, correctly-described file on Dispose(): the last partial frame is padded and flushed there, and the closing page records the true sample count so a decoder trims that padding instead of playing it. An undisposed writer leaves a file missing its tail that misreports its length.
• 48 kHz is not negotiable on the way out. Opus decodes at 48 kHz whatever the file says. The rate in an Opus header is the rate the encoder was handed — commonly 16000 for a messenger voice note — and RFC 7845 marks it informational. OpusFileReader.WaveFormat is therefore always 48 kHz; the declared value is available as EncoderInputSampleRate.
• Mono and stereo only. Channel mapping family 0. Multichannel Opus (family 1) is declined with a clear message rather than mis-mapped.

License

The project is licensed under the BSD 3-Clause License. see: https://en.wikipedia.org/wiki/BSD_licenses

The Opus codec itself is vendored from the Concentus project and carries the same BSD-3-Clause terms; THIRD-PARTY-NOTICES.txt reproduces that licence in full, names every copyright holder, and records exactly what was vendored and what was changed.