/**
 * OpenAI Text-to-Speech Handler
 *
 * Implementation of TTS using OpenAI's TTS API.
 *
 * @module voice/providers/OpenAITTS
 */
import type { TTSChunk, TTSHandler, TTSOptions, TTSResult, TTSVoice } from "../../types/index.js";
export declare class OpenAITTS implements TTSHandler {
    private readonly apiKey;
    private readonly baseUrl;
    /**
     * Maximum text length (4096 characters)
     */
    readonly maxTextLength = 4096;
    /**
     * Available voices
     */
    private static readonly VOICES;
    constructor(apiKey?: string);
    isConfigured(): boolean;
    getVoices(languageCode?: string): Promise<TTSVoice[]>;
    private requireApiKey;
    private prepareRequest;
    /**
     * Issue the speech request and reject non-2xx responses.
     *
     * `onHeaders` runs as soon as the request settles, before the response body
     * is touched at all. The buffered path clears its request timeout there,
     * which is where it has always been cleared: the 30-second bound covers
     * getting a response, not downloading one. The native path passes no
     * callback, keeping its own timeout armed across the body reads it owns.
     */
    private createSpeechResponse;
    private synthesisError;
    synthesize(text: string, options?: TTSOptions): Promise<TTSResult>;
    /**
     * Stream one segment's audio as the response body arrives.
     *
     * Returns `undefined` for any format without direct wire proof of
     * incremental delivery, which selects the buffered `synthesize()` path.
     *
     * Every non-empty body read is yielded as soon as it is available and
     * carries `isFinal: false`: assigning finality here would require a
     * one-read lookahead, delaying every fragment by a full body read, and
     * `TTSProcessor` recomputes finality globally anyway.
     */
    synthesizeStream(text: string, options?: TTSOptions): AsyncIterable<TTSChunk> | undefined;
    /**
     * Map TTSAudioFormat to OpenAI response_format.
     *
     * OpenAI's /audio/speech accepts mp3, opus, aac, flac, wav and pcm. This map
     * previously stopped at mp3/wav/ogg/opus/pcm16, so `flac` — a valid
     * TTSAudioFormat *and* a real OpenAI response_format — was treated as
     * unsupported and silently downgraded to mp3 (#479). A caller who asked for
     * lossless got lossy, and the only signal was a warn-level log.
     *
     * Formats OpenAI genuinely cannot produce still coerce to mp3 with a warning.
     */
    private mapFormat;
    /**
     * Get sample rate for format
     */
    private getSampleRate;
    /**
     * Map the OpenAI `response_format` string back to the canonical
     * `TTSAudioFormat` so `TTSResult.format` reflects what the API actually
     * returned (mapFormat() coerces unsupported requests to "mp3"). Note:
     * OpenAI returns Ogg-Opus for both "ogg" and "opus" requests — both
     * surface as "opus" since the bytes are an .ogg/Opus container.
     */
    private effectiveFormat;
}