Smallest AI Streaming API

openapi: 3.2.0
info:
  title: Smallest AI Waves Streaming API
  description: The Smallest AI Waves text-to-speech API. Generates natural speech from text using the Lightning family of models with sub-100ms latency, streams audio in realtime over Server-Sent Events, lists prebuilt voices, and clones custom voices from short audio samples. All endpoints are authenticated with a Bearer API key. The realtime bidirectional WebSocket transport for streaming TTS is modeled in the companion AsyncAPI document (asyncapi/smallest-ai-asyncapi.yml).
  termsOfService: https://smallest.ai/terms
  contact:
    name: Smallest AI Support
    url: https://smallest.ai/
    email: support@smallest.ai
  version: '1.0'
servers:
- url: https://waves-api.smallest.ai/api/v1
  description: Waves production API
security:
- bearerAuth: []
tags:
- name: Streaming
  description: Realtime streaming speech synthesis.
paths:
  /lightning-v2/get_speech/stream:
    post:
      operationId: streamSpeech
      tags:
      - Streaming
      summary: Stream synthesized speech (SSE).
      description: Streams synthesized speech in realtime using the Lightning v2 model. The response is an HTTP Server-Sent Events stream whose `data:` frames each carry a JSON object containing a base64-encoded audio chunk; a final frame signals completion. The same path is also available as a bidirectional WebSocket (wss) endpoint - see the AsyncAPI document.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/StreamSpeechRequest'
      responses:
        '200':
          description: Server-Sent Events stream of base64 audio chunks.
          content:
            text/event-stream:
              schema:
                $ref: '#/components/schemas/AudioStreamChunk'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '422':
          $ref: '#/components/responses/ValidationError'
        '429':
          $ref: '#/components/responses/RateLimited'
components:
  schemas:
    AudioStreamChunk:
      type: object
      description: JSON payload carried in each SSE `data:` frame. Frames carry a base64 audio chunk until a final frame sets `done` to true.
      properties:
        audio:
          type: string
          format: byte
          description: Base64-encoded raw PCM audio chunk.
        done:
          type: boolean
          description: True on the final frame to indicate the stream has completed.
    Error:
      type: object
      properties:
        status:
          type: string
          description: Error status indicator.
        message:
          type: string
          description: Human-readable error message.
        error:
          type: string
          description: Error code or detail, when present.
    StreamSpeechRequest:
      type: object
      required:
      - text
      - voice_id
      properties:
        text:
          type: string
          description: The text to stream as speech.
        voice_id:
          type: string
          description: Identifier of the voice to synthesize with.
          example: meher
        model:
          type: string
          description: The Lightning streaming model pool.
          default: lightning-v2
        sample_rate:
          type: integer
          description: Output audio sample rate in Hz.
          default: 24000
        speed:
          type: number
          format: float
          description: Speech rate multiplier; 1.0 is normal speed.
          default: 1.0
        language:
          type: string
          description: Language code for synthesis.
          default: en
  responses:
    RateLimited:
      description: Too many requests; the account rate limit was exceeded.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    ValidationError:
      description: The request body failed validation.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    Unauthorized:
      description: Missing or invalid API key.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      description: 'Pass your Waves API key as a Bearer token in the Authorization header: `Authorization: Bearer <SMALLEST_API_KEY>`.'