MidiFileReader.cs

using System.Reflection;
using Gondwana.Audio.NAudio;
using MeltySynth;
using Microsoft.Extensions.Logging;
using NAudio.Wave;
 
namespace Gondwana.Audio.Midi;

public static class MidiFileReader
{
    private static readonly Lazy<SoundFont> _soundFont = new(() =>
    {
        var assembly = Assembly.GetExecutingAssembly();
        using var stream = assembly.GetManifestResourceStream("Gondwana.Audio.Midi.TimGM6mb.sf2")
            ?? throw new InvalidOperationException("Embedded SoundFont 'TimGM6mb.sf2' not found.");
 
        return new SoundFont(stream);
    });

    public static SoundFont SoundFont => _soundFont.Value;

    internal static void RegisterDefaultReaders()
    {
        NAudioReaderRegistry.Register(".mid", CreateReader);
        NAudioReaderRegistry.Register(".midi", CreateReader);
        Engine.Logger.LogInformation("Registered Gondwana.Audio.Midi readers with the NAudio backend.");
    }

    public static WaveStream CreateReader(Stream stream)
    {
        using var buffer = new MemoryStream();
        stream.CopyTo(buffer);
        buffer.Position = 0;
 
        var synth = new Synthesizer(SoundFont, 44100);
        var midi = new MidiFile(buffer);
        var sequencer = new MidiFileSequencer(synth);
        sequencer.Play(midi, loop: false);
 
        var provider = new SynthesizerSampleProvider(sequencer, synth, midi, loop: false);
        return new WaveProviderToWaveStream(provider.ToWaveProvider(), midi.Length.TotalSeconds, provider.Seek);
    }
}