Audio

Sliver’s SoundManager is a small wrapper around the Web Audio API (AudioContext).

You typically:

1. create a single SoundManager for your game
2. preload sounds (SFX + music) with loadSound
3. “unlock” audio after a user interaction
4. use playSound for one-shots and playSong for background music

Getting the SoundManager

SoundManager is available through the GameContext:

const sound = game.getContext().getSoundManager();

Your Game instance receives a soundManager in its constructor options, so you usually create it once and pass it in:

import { Game, SoundManager } from "sliver-engine";

const soundManager = new SoundManager();

const game = new Game({
  canvas,
  scenes,
  soundManager: soundManager,
});

Unlocking audio (required by browsers)

Browsers block audio autoplay. Until the user clicks/taps/presses a key, the underlying AudioContext is typically “suspended”.

Call unlock() from a user interaction handler (recommended), once, as early as possible:

window.addEventListener("pointerdown", async () => {
  await game.getContext().getSoundManager().unlock();
});

I recommend integrating this unlock into your game in the following way:

• Your start scene has nothing but a button for start game
• Clicking that button transitions to the next scene and unlocks the audio

class MyButton extends GameObject {
  // {...}

  @onClick((self) => {
    self.getContext().getSoundManager().unlock();
  })
  override handleEvent(event: GameEvent) {
    super.handleEvent(event);
  }
}

// or

class MyButton extends GameObject {
  // {...}

  @onClick((self) => {
    self.getContext().getSoundManager().playSound("button_click");
    // If the first audio that's played comes from a user
    // interaction, the unlock happens automatically
  })
  override handleEvent(event: GameEvent) {
    super.handleEvent(event);
  }
}

Why this matters:

• unlock() connects the internal masterGain to the audio output and resumes the AudioContext.
• playSound() / playSong() try to unlock automatically when needed, but they don’t await it, so your very first sound is more reliable if you unlock explicitly on input.

Preloading sounds

Load audio files into an in-memory library (decoded into an AudioBuffer):

const sound = game.getContext().getSoundManager();

await sound.loadSound(
  "jump",
  new URL("/audio/jump.wav", window.location.href),
  ["sfx", "player"]
);

await sound.loadSound(
  "bgm:forest",
  new URL("/audio/forest-theme.ogg", window.location.href),
  ["music"]
);

Notes:

• loadSound(name, url, tags?) fetches the asset and decodes it. If the fetch fails, it throws with the HTTP status.
• tags are stored with the sound entry (useful for your own filtering/organization via getLoadedSounds()).
• [TODO] tags will also be used to create a gain control for each tag in the future

Master volume

SoundManager routes all sounds through a master gain node, so you can implement global volume/mute easily:

const sound = game.getContext().getSoundManager();

sound.setMasterGain(0.6); // clamps to >= 0
console.log(sound.getMasterGain()); // -> 0.6

Per-sound default volume

Each loaded sound keeps a default volume (used when you don’t pass an explicit volume to playSound / playSong):

sound.setSoundVolume("jump", 0.3); // clamps to >= 0
console.log(sound.getSoundVolume("jump")); // -> 0.3

This is a good place to normalize loud assets so your call sites can stay simple.

Playing one-shot sound effects

Use playSound(name, options) for SFX. It returns a small controller with a stop() method.

const sfx = sound.playSound("jump", {
  volume: 0.8,
  playbackRate: 1.1,
});

// ...later (optional)
sfx.stop();

Useful options

• loop: repeat until stopped (defaults to false)
• playbackRate: speed/pitch (defaults to 1)
• wait: delay before playing (seconds)
• start: offset into the audio file (seconds)
• end: stop at an absolute time in the file (seconds)
• duration: how long to play (seconds). If present, it takes precedence over end.

Example: play only a short “blip” segment, after a delay:

sound.playSound("ui:beep", {
  wait: 0.05,
  start: 0.12,
  duration: 0.08,
});

Why duration wins over end: it’s often easier to express “play 80ms from here” than to compute an absolute end time when you change start.

Playing and controlling background music (“songs”)

Use playSong(name, options) for tracked background music.

Behavior:

• If you request the same song that’s already playing, nothing changes and you get the existing controller back.
• If you request a different song, the previous song is stopped and the new one starts.

By default, songs loop (loop defaults to true for playSong).

Fading between songs

playSong supports fade transitions (in seconds) via fade, fadeIn, and fadeOut:

sound.playSong("bgm:forest", { volume: 0.5, fade: 0.6 });

// Later, cross-fade to another track
sound.playSong("bgm:cave", { volume: 0.5, fadeOut: 0.6, fadeIn: 0.8 });

To stop the current song:

sound.stopSong({ fadeOut: 0.5 });

Or use the controller returned by playSong:

const song = sound.playSong("bgm:forest");
song.stop({ fadeOut: 0.5 });

Introspection and debugging

console.log(sound.getCurrentSongName()); // string | undefined
console.log(Object.keys(sound.getLoadedSounds())); // names you loaded