import type { ResolvedDevice } from "../device.js";
import type { PcmAudio } from "../platform.js";
import type { SynthesisEngine, SynthesisRequest } from "./types.js";
/** Dimensionality of the descriptor {@link PlaceholderEngine.embed} produces. */
export declare const VOICE_EMBEDDING_SIZE = 4;
export interface PlaceholderEngineOptions {
    /**
     * Sample rate of the rendered audio.
     *
     * @defaultValue 24000
     */
    sampleRate?: number;
}
/**
 * A dependency-free stand-in for a neural TTS model.
 *
 * It extracts a coarse timbre descriptor (pitch, brightness, loudness,
 * roughness) from reference audio and renders text as a harmonic tone driven
 * by that descriptor. The output is intelligible as *speech-shaped* audio, not
 * as speech: it exists so the whole pipeline — cloning, storage, chunking,
 * streaming, playback — can be built and tested before an ONNX Runtime Web
 * backend lands.
 *
 * Replace it by passing your own {@link SynthesisEngine} to `VoxShot.create`.
 */
export declare class PlaceholderEngine implements SynthesisEngine {
    #private;
    readonly name = "placeholder";
    readonly sampleRate: number;
    constructor(options?: PlaceholderEngineOptions);
    /** The device this engine was loaded on, if any. */
    get device(): ResolvedDevice | undefined;
    load(device: ResolvedDevice): Promise<void>;
    embed(audio: PcmAudio): Promise<Float32Array>;
    synthesize(request: SynthesisRequest): Promise<Float32Array>;
    dispose(): Promise<void>;
}
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