experimental_streamSpeech

Streams speech audio from text, or from an array or stream of text deltas and text parts, using a speech model with streaming support.

import { experimental_streamSpeech as streamSpeech } from 'ai';
import { elevenLabs } from '@ai-sdk/elevenlabs';

const result = streamSpeech({
  model: elevenLabs.speech('eleven_flash_v2_5'),
  text: 'Hello, world!',
});

for await (const chunk of result.audioStream) {
  // Uint8Array audio bytes
}

Import

import { experimental_streamSpeech as streamSpeech } from "ai"

API Signature

Parameters

• model (SpeechModel): The speech model to use. The model must implement the experimental streaming speech extension (Experimental_StreamingSpeechModelV4).
• text (string | Iterable<string | Experimental_SpeechTextPart> | AsyncIterable<string | Experimental_SpeechTextPart> | ReadableStream<string | Experimental_SpeechTextPart>): The text to convert to speech: a complete string, or an array, iterable, or stream of text deltas (e.g. the textStream of streamText) and/or text parts { type: 'text', text, voice?, providerOptions? }. A part's voice selects its speaker on providers that support several voices per stream; single-voice providers error the stream when a part's voice differs from the call's voice. The end of the stream ends the input.
• voice? (string): The voice to use for speech generation.
• outputFormat? ({ type: string; rate?: number }): The format of the output audio chunks, e.g. { type: 'audio/pcm', rate: 24000 } or { type: 'audio/mpeg' }. Supported formats are provider-specific.
• instructions? (string): Instructions for the speech generation.
• speed? (number): The speed of the speech generation.
• language? (string): The language for speech generation (ISO 639-1 code), or "auto". Provider support varies.
• providerOptions? (Record<string, JSONObject>): Additional provider-specific options.
• abortSignal? (AbortSignal): An optional abort signal to cancel the call.
• headers? (Record<string, string>): Additional HTTP/WebSocket headers, if supported by the provider.
• includeRawChunks? (boolean): When true, the provider includes raw provider chunks in fullStream as raw parts.
• onError? ((event: { error: unknown }) => void | PromiseLike<void>): Called for each error part the provider reports. Defaults to console.error.

Returns

• audioStream (AsyncIterableStream<Uint8Array>): Audio bytes in generation order. Shares one live stream with fullStream: only one of them can be accessed, once, before any result promise. error parts are skipped (they are reported via onError); the stream errors only when the speech stream itself fails.
• fullStream (AsyncIterableStream<Experimental_SpeechStreamPart>): A single-consumer live stream of audio (with audio: Uint8Array and audioFormat), raw, and error parts. Error parts are not fatal; the stream continues after them.
• usage (Promise<{ inputCharacters?: number; inputTokens?: number; outputTokens?: number; raw?: JSONObject }>): Usage information for the call, if known.
• warnings (Promise<Warning[]>): Warnings for the call, e.g. unsupported settings. Resolves when the provider emits the stream start.
• responses (Promise<Array<SpeechModelResponseMetadata>>): Response metadata (timestamp, model ID, headers, body).
• providerMetadata (Promise<Record<string, JSONObject>>): Additional provider-specific metadata.

Errors

• UnsupportedFunctionalityError is thrown synchronously when the model does not support streaming speech.
• InvalidArgumentError is thrown synchronously when text is not a string, an iterable or async iterable, or a readable stream.
• Provider error parts are not fatal. They appear in fullStream, are skipped by audioStream, and are passed to onError.
• If the stream ends without audio, the result rejects with NoSpeechGeneratedError, whose cause is the last provider error part.
• If the stream stops after audio but before it finished, the result rejects with the last provider error part, or with a StreamProviderError.
• If the provider call fails (for example an authentication error), the result rejects with that error. Cancelling or aborting rejects with the cancellation or abort reason.

Wire format (experimental)

Streaming speech over WebSocket is serialized with the experimental speech-stream envelope defined in @ai-sdk/provider-utils (experimental_parseSpeechStreamClientFrame, experimental_serializeSpeechStreamPart, experimental_parseSpeechStreamPart): the client sends one speech-stream.start TEXT frame, input text as speech-stream.text-delta TEXT frames (each carrying its text part's voice and providerOptions), and a speech-stream.text-done TEXT frame; each server TEXT frame is one JSON-serialized speech stream part with base64 audio. AI Gateway implements the server side of this envelope.