OpenAL Soft Bindings for C#

Modern, high-performance C# bindings for OpenAL Soft, with managed wrappers for ease of use.

Features

• Modern C# Interop: Uses LibraryImport and Span<T> for optimal performance
• Zero-Allocation Design: Leverages stack allocation and spans to minimize heap allocations
• Complete Coverage: Supports OpenAL 1.0, OpenAL 1.1, and:
  • Effects Extensions (EFX) for audio effects and filters
  • OpenAL Extensions (ALEXT, SOFT) for latest functionality
  • Debug extensions for development
• Managed Wrappers: High-level managed classes for common scenarios:
  • ALDevice for device management
  • ALContext for context creation and management
  • ALCaptureDevice for microphone input
  • ALSource for sources
  • ALFilter and ALReverbEffect for filters and effects

Requirements

• .NET 8.0 or later
• OpenAL Soft library:
  • soft_oal.dll on Windows
  • libopenal.so on Linux
  • libopenal.1.dylib on OSX

Quick Start

Basic Setup

using OpenAL;
using OpenAL.managed;

// Get all devices
var deviceNames = AL.GetStringList(IntPtr.Zero, AL.ALC_ALL_DEVICES_SPECIFIER);

// Open a device
var device = new ALDevice(deviceNames[0]);

// Create a context
var context = new ALContext(device, new ALContextSettings()
{
    HRTFEnabled = true,
    SampleRate = 48000
});

// Make the context current
context.MakeCurrent();

// Generate a buffer and source
uint buffer = AL.GenBuffer();
uint source = AL.GenSource();

// Load PCM data into the buffer
AL.BufferData(buffer, AL.AL_FORMAT_MONO16, pcmData, sampleRate);

// Configure and play the source
AL.Sourcei(source, AL.AL_BUFFER, (int)buffer);
AL.SourcePlay(source);

// Cleanup
AL.DeleteSource(source);
AL.DeleteBuffer(buffer);

context.Destroy();
device.Close();

Effects (EFX)

// Generate an effect and auxiliary send
uint effect = AL.GenEffect();
uint auxSlot = AL.GenAuxiliaryEffectSlot();

// Configure reverb effect
AL.Effecti(effect, AL.AL_EFFECT_TYPE, AL.AL_EFFECT_REVERB);
AL.Effectf(effect, AL.AL_REVERB_GAIN, 0.7f);
AL.Effectf(effect, AL.AL_REVERB_DECAY_TIME, 2.5f);

// Attach effect to auxiliary slot
AL.AuxiliaryEffectSloti(auxSlot, AL.AL_EFFECTSLOT_EFFECT, (int)effect);

// Connect source to effect slot
AL.Source3i(source, AL.AL_AUXILIARY_SEND_FILTER, (int)auxSlot, 0, AL.AL_FILTER_NULL);

3D Spatialised Audio

// Set listener orientation using span
Span<float> orientation = [ 0f, 0f, -1f, 0f, 1f, 0f ];
AL.Listenerfv(AL.AL_ORIENTATION, orientation);

// Position a source in 3D space
AL.Source3f(source, AL.AL_POSITION, 5f, 0f, -10f);
AL.Source3f(source, AL.AL_VELOCITY, 0f, 0f, 1f);

// Configure distance model
AL.DistanceModel(AL.AL_INVERSE_DISTANCE_CLAMPED);
AL.Sourcef(source, AL.AL_REFERENCE_DISTANCE, 1f);
AL.Sourcef(source, AL.AL_MAX_DISTANCE, 100f);

Architecture

The library is organized into several layers:

Internal Bindings (internal/)

Low-level P/Invoke declarations that directly wrap OpenAL native functions:

• ALBindings.cs - Core OpenAL
• ALCBindings.cs - Context management
• EFXBindings.cs - Effects and filters
• ALEXTBindings.cs - OpenAL extensions
• DebugBindings.cs - Debug callback

Public API (public/)

Clean C# wrappers for functions and constants:

• AL.cs - Core OpenAL
• ALC.cs - Context management
• EFX.cs - Effects and filters
• ALEXT.cs - OpenAL extensions
• *Constants.cs - OpenAL constants

Managed Wrappers (managed/)

High-level classes for common use cases:

• ALDevice.cs / ALCaptureDevice.cs - Device lifecycle management
• ALContext.cs - Context creation with HRTF support
• ALSource.cs - Audio source management
• ALFilter.cs - Filter management
• ALReverbEffect.cs - Reverb effect helpers

Thread Safety

OpenAL's error state is per-context rather than per-thread. For multithreaded applications:

• Create separate contexts for different threads
• Use synchronization when sharing contexts
• Consider using thread-local contexts for audio processing threads

License

MIT No Attribution

Copyright 2025 Vercidium Pty Ltd

See license.txt for full license text.

Contributing

Contributions are welcome! The project follows modern C# conventions:

• Use of LibraryImport over DllImport
• Span-based APIs where appropriate

Resources

• OpenAL Soft Repository
• Extensions and PDF Specification

Status

This is an actively developed project. Current focus areas:

• Improving managed wrapper APIs
• Adding comprehensive examples