/**
 * Audio backend — the shared internal surface every other audio module
 * (procedural, playback) builds on. Keeps the Howler reference and the
 * cross-module mutable state in one place so the public surface modules
 * stay backend-agnostic.
 *
 * Not part of the public `me.audio.*` API — the two getters
 * `getAudioContext` / `getMasterGain` are re-exported from `audio.ts`
 * for end users; everything else (the `state` object, `soundLoadError`)
 * is internal.
 */
import { Howl } from "howler";
/**
 * Whether to stop on an audio loading error.
 *
 * When `true`, melonJS throws an exception and aborts loading.
 * When `false`, melonJS disables sound and logs a warning to the console.
 * @default true
 */
export declare let stopOnAudioError: boolean;
/**
 * Cross-module mutable state. A single object so multiple consumers
 * can read and mutate the same fields without the "ESM `let` exports
 * don't share writes across modules" footgun.
 *
 * Fields:
 * - `tracks` — loaded Howl instances keyed by logical sound name.
 *   `Howl | undefined` because missing keys return undefined at runtime
 *   even though the type signature wouldn't normally admit it.
 * - `currentTrackId` — the name of the currently-playing track managed
 *   by the `playTrack` / `stopTrack` helpers.
 * - `retryCounter` — retry counter for `soundLoadError`'s back-off.
 * - `audioExts` — the active list of audio formats set by `init`.
 * @ignore
 */
export declare const state: {
    tracks: Record<string, Howl | undefined>;
    currentTrackId: string | null;
    retryCounter: number;
    audioExts: string[];
};
/**
 * Look up a loaded `Howl` instance by logical name, or throw a
 * uniform "audio clip X does not exist" error if it isn't loaded.
 * Used by every per-clip helper across `playback.ts` / `audio.ts` so
 * the error contract stays identical across the whole surface.
 * @ignore
 */
export declare function getSoundOrThrow(sound_name: string): Howl;
/**
 * Event listener callback on load error. Retries the load up to 3
 * times, then either throws or disables audio (depending on the
 * `stopOnAudioError` flag re-exported from `audio.ts`).
 * @ignore
 */
export declare const soundLoadError: (sound_name: string, onerror_cb?: () => void, stopOnError?: boolean) => void;
/**
 * Returns the underlying WebAudio `AudioContext` used by the audio
 * module (the same one shared with file-based playback), or `null` if
 * audio is disabled or no compatible WebAudio implementation is
 * available.
 *
 * Use this when you need to build a custom WebAudio graph — procedural
 * SFX, custom filters / spatial nodes, audio analysis — without
 * spawning a second context. Browsers throttle or refuse multiple
 * `AudioContext` instances on the same page and each has its own
 * suspend-until-gesture state, so sharing matters.
 *
 * The context is lazily created on first access; the call also returns
 * the cached instance on every subsequent call.
 * @category Audio
 */
export declare function getAudioContext(): AudioContext | null;
/**
 * Return the audio module's master gain node — the single `GainNode`
 * every playback path runs through on its way to `ctx.destination`,
 * and the lever that {@link setVolume} / {@link muteAll} manipulate.
 *
 * Connect to this node (instead of `ctx.destination`) whenever you
 * build a custom WebAudio graph and want the result to respect the
 * engine's mute / volume state. Returns `null` when audio is disabled
 * or unavailable.
 * @category Audio
 */
export declare function getMasterGain(): GainNode | null;
/**
 * Get the audio module's global volume.
 * @ignore
 */
export declare function getGlobalVolume(): number;
/**
 * Set the audio module's global volume.
 * @ignore
 */
export declare function setGlobalVolume(v: number): void;
/**
 * Mute or unmute the audio module globally.
 * @ignore
 */
export declare function setGlobalMuted(muted: boolean): void;
/**
 * Whether the audio module is currently muted globally.
 * @ignore
 */
export declare function isGlobalMuted(): boolean;
/**
 * Stop every playing sound on every channel.
 * @ignore
 */
export declare function stopAllPlayback(): void;
/**
 * Whether the given audio codec is supported by the backend / browser.
 * @ignore
 */
export declare function hasCodec(codec: string): boolean;
/**
 * Whether at least one audio backend (HTML5 or WebAudio) is available.
 * @ignore
 */
export declare function isAudioAvailable(): boolean;
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