/**
 * A cross-environment audio-decoding {@link @nhtio/adk/batteries/media/contracts!MediaEngine}
 * backed by the `audio-decode` package (pure JS/WASM codecs — no ffmpeg, no native bindings;
 * works in Node and browsers).
 *
 * @module @nhtio/adk/batteries/media/engines/audio_decode
 *
 * @remarks
 * Declares two convert capabilities: audio containers to the virtual `pcm` token (mp3 /
 * m4a-aac / ogg-vorbis / opus / flac / wav), downmixed to mono; and a generation edge —
 * `EMPTY_MIME` → wav. Audio bytes are just bytes in a documented envelope: the generated
 * seed is a canonical 44-byte RIFF/WAVE header plus one second of 16-bit mono silence at
 * 44100 Hz, written by a dependency-free helper (generation never loads the decode peer).
 * The PCM output reports the SOURCE sample rate in `meta.sampleRate` — the pipeline's
 * transcribe step resamples to the 16 kHz transcription engines expect. For exotic
 * containers, compose an ffmpeg-backed engine instead; the capability declaration is the
 * seam.
 *
 * `audio-decode` is an optional peer dependency, lazily imported on first actual use.
 */
import type { MediaEngine } from "../contracts";
/**
 * The decoded shapes audio-decode resolves to. Some codecs return an AudioBuffer-compatible
 * object (`numberOfChannels` + `getChannelData`); others (e.g. the wav path in Node) return a
 * plain `{ channelData: Float32Array[], sampleRate }` record. The engine normalizes both.
 */
export interface AudioBufferLike {
    /** Channel count when the AudioBuffer-compatible shape is returned. */
    numberOfChannels?: number;
    /** Sample rate of the decoded audio, in Hz. Present on both shapes. */
    sampleRate: number;
    /** Per-channel sample accessor on the AudioBuffer-compatible shape. */
    getChannelData?(channel: number): Float32Array;
    /** Raw per-channel sample arrays on the plain-record shape. */
    channelData?: Float32Array[];
}
/** The decode function shape the `audio-decode` package exports. */
export type AudioDecodeFn = (bytes: Uint8Array | ArrayBuffer) => Promise<AudioBufferLike>;
/** Options for {@link audioDecodeEngine}. */
export interface AudioDecodeEngineOptions {
    /** Override the module resolution. Default: `import('audio-decode')`. */
    audioDecode?: () => AudioDecodeFn | {
        default: AudioDecodeFn;
    } | Promise<AudioDecodeFn | {
        default: AudioDecodeFn;
    }>;
}
/**
 * Construct the audio-decode-backed engine.
 *
 * @param options - Optional module resolver override.
 * @returns The engine.
 */
export declare const audioDecodeEngine: (options?: AudioDecodeEngineOptions) => MediaEngine;