Voile/Voile/Source/Audio/FmodAudioBackend.cs

using FMOD;
using System.Runtime.InteropServices;

namespace Voile.Audio
{
    public class FmodAudioBackend : AudioBackend
    {
        public override void Initialize()
        {
            CreateSystem();
            _loadedSounds = new Dictionary<string, FMOD.Sound>();
            _channelGroups = new Dictionary<string, ChannelGroup>();

            CreateBus("Master");
        }
        public override void Update() => _system.update();

        public override void PlaySound(Sound sound, string bus = "Master", float pitch = 1, float volume = 1)
        {
            int channels = 0;

            if (sound.Format == SoundFormat.Mono)
            {
                channels = 1;
            }
            else if (sound.Format == SoundFormat.Stereo)
            {
                channels = 2;
            }

            var channel = PlaySoundFromBuffer(sound.Path, (int)sound.BufferSize, channels, sound.SampleRate, sound.Buffer, GetChannelGroup(bus));
            channel.setVolume(volume);
            channel.setPitch(pitch);
        }

        public override void CreateBus(string busName)
        {
            ChannelGroup channelGroup;
            _system.createChannelGroup(busName, out channelGroup);
            _channelGroups.Add(busName, channelGroup);
        }

        public override void SetBusVolume(string busName, float volume)
        {
            var channel = GetChannelGroup(busName);
            channel.setVolume(volume);
        }

        public override float GetBusVolume(string busName)
        {
            float volume;
            GetChannelGroup(busName).getVolume(out volume);
            return volume;
        }

        public override void AddBusEffect<T>(T effect, string bus = "Master")
        {
            var channelGroup = GetChannelGroup(bus);
            DSP dsp;

            switch (effect)
            {
                case AudioEffectReverb:
                    dsp = CreateReverbDsp(effect as AudioEffectReverb);
                    break;
                default:
                    _system.createDSPByType(DSP_TYPE.UNKNOWN, out dsp);
                    break;
            }

            channelGroup.addDSP(0, dsp);
        }

        protected override void Shutdown()
        {

        }

        private DSP CreateReverbDsp(AudioEffectReverb effectReverb)
        {
            DSP dsp;
            _system.createDSPByType(DSP_TYPE.SFXREVERB, out dsp);
            return dsp;
        }

        private void CreateSystem()
        {
            var result = FMOD.Factory.System_Create(out _system);
            _system.init(128, INITFLAGS.NORMAL, 0);
        }

        private Channel PlaySoundFromBuffer(string path, int length, int channels, int sampleRate, byte[] buffer, ChannelGroup channelGroup)
        {
            Channel fmodChannel;
            FMOD.Sound fmodSound = IsLoaded(path) ? GetSoundFromLoaded(path) : CreateSound(length, channels, sampleRate, path, buffer);

            _system.playSound(fmodSound, channelGroup, false, out fmodChannel);

            return fmodChannel;
        }


        private FMOD.Sound GetSoundFromLoaded(string path) => _loadedSounds[path];
        private bool IsLoaded(string path) => _loadedSounds.ContainsKey(path);

        private FMOD.Sound CreateSound(int length, int channels, int sampleRate, string path, byte[] buffer)
        {
            FMOD.Sound sound;
            CREATESOUNDEXINFO info = new CREATESOUNDEXINFO()
            {
                numchannels = channels,
                defaultfrequency = sampleRate,
                format = SOUND_FORMAT.PCM16,
                length = (uint)length,
                cbsize = Marshal.SizeOf(typeof(CREATESOUNDEXINFO))
            };

            var result = _system.createSound(buffer, FMOD.MODE.OPENMEMORY | FMOD.MODE.OPENRAW | FMOD.MODE.CREATESAMPLE, ref info, out sound);
            AddToLoaded(path, sound);
            return sound;
        }

        private void AddToLoaded(string path, FMOD.Sound sound) => _loadedSounds.Add(path, sound);

        private ChannelGroup GetChannelGroup(string busName)
        {
            return _channelGroups[busName];
        }

        private FMOD.System _system;

        // TODO: use a different key for the dictionary, paths are not good :( (waste of memory lol)
        private Dictionary<string, FMOD.Sound> _loadedSounds;
        private Dictionary<string, ChannelGroup> _channelGroups;
    }
}