/**
 * Whistle — the built-in, zero-config, on-device speech-to-text engine.
 *
 * Runs Cactus's Whistle model (17 MB) on the Cactus "needle" engine, an
 * Emscripten WebAssembly build, inside a `worker_threads` Worker. No API key,
 * no network after the first use, no native addon: it is the STT provider
 * NeuroLink falls back to when no other one is configured.
 *
 * **Files.** `needle.js`, `needle.wasm` and `whistle.cact` (~17.9 MB in all)
 * are downloaded from pinned Hugging Face revisions on first use, checked
 * against SHA-256 and kept in the model directory:
 * `credentials.stt.whistle.modelDir` → `NEUROLINK_WHISTLE_DIR` →
 * `$NEUROLINK_MODEL_DIR/whistle` → `~/.neurolink/models/whistle`. Set
 * `NEUROLINK_WHISTLE_AUTO_DOWNLOAD=0` (or `autoDownload: false`) to forbid the
 * download; a missing file then fails with an error naming each file, where it
 * goes and where to get it.
 *
 * **Languages.** English, German, French, Spanish, Italian, Dutch and Polish
 * (`en de fr es it nl pl`). `options.language` accepts a code or a locale
 * (`"de-DE"`); `"auto"`, omitted or any other language lets the engine detect
 * one of the seven.
 *
 * **Limits.** The engine reads 30 s per call; longer audio is cut at the
 * quietest 20 ms frame near every 24 s mark and the word times are offset
 * back onto the whole recording. One hour per request. Roughly 0.5 s of CPU
 * per 10 s of audio on a laptop core; one warm worker per handler instance,
 * requests served in order.
 *
 * **Keyword biasing.** `options.vocabulary` is passed to the engine as
 * keywords only when `options.model` is `"whistle-keywords"` or
 * `NEUROLINK_WHISTLE_KEYWORDS=1` — the engine can loop on long keyword lists,
 * so it is opt-in and capped at {@link MAX_KEYWORDS} entries.
 *
 * **Formats.** WAV (any PCM/float layout, rate and channel count) and raw
 * `pcm16` are decoded in-process; mp3, m4a, ogg/opus, webm, flac and mp4 need
 * ffmpeg (`ffmpeg-static`, `FFMPEG_PATH` or `ffmpeg` on PATH).
 *
 * **Streaming.** Native: `transcribeStream()` feeds the engine's own streaming
 * decoder about a second at a time, on a dedicated worker per stream. Each
 * step yields a final segment for the words two passes agreed on, and an
 * interim segment for the unconfirmed tail. Input frames are PCM16LE mono at
 * `options.sampleRate` (default 16 kHz).
 *
 * **Accuracy.** A 17 MB model: good on clear speech in its seven languages,
 * noticeably behind cloud engines and large Whisper-class models on accents,
 * noise, crosstalk, names and jargon. Use a dictionary/correction pass, or a
 * cloud provider, where that matters.
 *
 * @module voice/providers/WhistleSTT
 */
import type { STTCredentials, STTHandler, STTLanguage, STTOptions, STTResult, TranscriptionSegment, TTSAudioFormat } from "../../types/index.js";
export declare class WhistleSTT implements STTHandler {
    /** One hour per request (16 kHz float samples: ~230 MB in memory). */
    readonly maxAudioDuration: number;
    /** The engine has its own streaming decoder. */
    readonly supportsStreaming = true;
    private readonly modelDir;
    private readonly autoDownload;
    private engine;
    constructor(slice?: STTCredentials["whistle"]);
    /**
     * True when the engine can run: its files are already in the model dir, or
     * it is allowed to fetch them. With `NEUROLINK_WHISTLE_AUTO_DOWNLOAD=0` (or
     * `autoDownload: false`) and no files, it reports unconfigured, so a caller
     * asserting "no STT backend" is not answered by a 17 MB download.
     */
    isConfigured(): boolean;
    describeConfiguration(): string;
    /** Directory the engine's files live in. */
    getModelDir(): string;
    getSupportedFormats(): TTSAudioFormat[];
    getSupportedLanguages(): Promise<STTLanguage[]>;
    /** Download/verify the files and start the worker now rather than on the first request. */
    warmUp(): Promise<void>;
    /** Stop the warm worker. The handler stays usable; the next call starts a new one. */
    dispose(): Promise<void>;
    transcribe(audio: Buffer | ArrayBuffer, options?: STTOptions): Promise<STTResult>;
    /**
     * Native streaming. `audioStream` yields PCM16LE mono frames at
     * `options.sampleRate` (default 16 kHz), any frame size. Yields a final
     * segment for each run of words the engine commits (times from the start of
     * the stream; join the finals with a space for the transcript) and an
     * interim segment carrying the unconfirmed tail whenever it changes.
     */
    transcribeStream(audioStream: AsyncIterable<Buffer>, options?: STTOptions): AsyncIterable<TranscriptionSegment>;
    private getEngine;
}