> ## Documentation Index > Fetch the complete documentation index at: https://docs.vidgo.ai/llms.txt > Use this file to discover all available pages before exploring further. # Gemini 3.8 Flash TTS > The Gemini 3.8 Flash TTS API turns a script or a two-speaker dialogue into WAV audio, with 30 preset voices and style instructions to steer delivery. > [!TIP] > > 1. After submission, a `task_id` will be returned. If you provided a `callback_url`, when the task status becomes `finished` or `failed`, a POST request will be sent to the `callback_url`. > 2. Regardless of whether `callback_url` is provided, you can retrieve the result through the unified [Query Task Status](https://docs.vidgo.ai/api-manual/task-management/status.md) endpoint. Gemini 3.8 Flash TTS is Google's highest-fidelity Gemini 3.8 text-to-speech model. It reads a script with one voice, or performs a two-speaker dialogue, and returns WAV audio. Choose from 30 preset voices, steer tone, pace and emotion with style instructions, and let the model detect the language (Google lists 130). It suits audiobooks, podcast-style conversations, studio narration and character dialogue. For high-volume, everyday speech with the same request fields, use [Gemini 3.8 Flash-Lite TTS](https://docs.vidgo.ai/api-manual/music-series/google-gemini-3-8-flash-lite-text-to-speech.md). Switch between them by changing `model`. ## Models * **google/gemini-3.8-flash/text-to-speech** — Gemini 3.8 Flash text-to-speech for single-voice narration and two-speaker dialogue. ## Features * Text-to-speech with one voice, or a scripted dialogue between two speakers. * 30 preset voices, set per request or per speaker. * Plain-language `style_instructions` for tone, pace, accent and emotion, globally or per dialogue turn. * Automatic language detection (Google lists 130 languages). * WAV audio output. ## Input modes * **Single speaker**: send `text` and, optionally, `voice` (default `Kore`). * **Two-speaker dialogue**: send exactly two `speakers` and a list of `turns`. Do not send top-level `text` or `voice` in this mode. ## Required parameters Single speaker: * `text` (string): The text to speak. Not blank. Two-speaker dialogue: * `speakers` (object\[]): Exactly two objects, each with only: * `speaker_id` (string): A non-empty alias, unique within the request, such as `host`. * `voice` (string): One of the [Voice Presets](#voice-presets). * `turns` (object\[]): At least one line, in speaking order: * `speaker_id` (string): Must match one of the two `speakers`. * `text` (string): What that speaker says. Not blank. * `style_instructions` (string, optional): Direction for this line only. ## Optional parameters * `voice` (string): Single-speaker mode only. One of the [Voice Presets](#voice-presets). Default `Kore`. * `style_instructions` (string): Global direction for the whole request, such as `Calm, warm documentary narration`. Works in both modes. * `enable_safety_checker` (boolean): Run the upstream safety checker. Default `true`. ## Output The finished task returns one WAV audio file in the `files` array of [Query Task Status](https://docs.vidgo.ai/api-manual/task-management/status.md) and the callback payload. The output format is fixed; there is no `output_format` field. ## Voice Presets `voice` and `speakers[].voice` accept these 30 values (case-sensitive): > [accordion] Supported voice values > > * `Achernar` > * `Achird` > * `Algenib` > * `Algieba` > * `Alnilam` > * `Aoede` > * `Autonoe` > * `Callirrhoe` > * `Charon` > * `Despina` > * `Enceladus` > * `Erinome` > * `Fenrir` > * `Gacrux` > * `Iapetus` > * `Kore` > * `Laomedeia` > * `Leda` > * `Orus` > * `Pulcherrima` > * `Puck` > * `Rasalgethi` > * `Sadachbia` > * `Sadaltager` > * `Schedar` > * `Sulafat` > * `Umbriel` > * `Vindemiatrix` > * `Zephyr` > * `Zubenelgenubi` ## Examples * **Single-speaker narration with style**: `voice: Charon` with a global `style_instructions` for slow documentary delivery. * **Two-speaker podcast dialogue**: `host` (`Kore`) and `guest` (`Puck`), with per-turn `style_instructions` on two lines and a `callback_url`. ## Notes * Credits are reserved at submission and depend on the billable character count: `text`, the global `style_instructions`, and every turn's `text` and `style_instructions`. Speaker IDs are not counted. A failed task is refunded in full. See the [pricing page](https://vidgo.ai/apis/api-pricing) for current rates. * [Gemini 3.8 Flash-Lite TTS](https://docs.vidgo.ai/api-manual/music-series/google-gemini-3-8-flash-lite-text-to-speech.md) is billed at a lower rate with the same fields. * Dialogue supports exactly two speakers. A third speaker, a `speaker_id` in `turns` that is not in `speakers`, or top-level `text`/`voice` in a dialogue request returns 400. * Put delivery directions in `style_instructions`, not in `text`; the model may read directions inside `text` aloud. * `output_format`, `language_code`, `temperature`, `seed` and timestamps are not supported on this endpoint, and neither are voice cloning or custom voices. ## OpenAPI ````yaml api-manual/music-series/google-gemini-3-8-flash-text-to-speech.json POST /api/generate/submit openapi: 3.0.0 info: title: Vidgo API - Gemini 3.8 Flash TTS description: >- The Gemini 3.8 Flash TTS API turns a script or a two-speaker dialogue into WAV audio, with 30 preset voices and style instructions to steer delivery. version: 1.0.0 servers: - url: https://api.vidgo.ai description: Production server security: - BearerAuth: [] paths: /api/generate/submit: post: tags: - Audio Series summary: Gemini 3.8 Flash TTS description: >- Send `text` (plus optional `voice`) for one speaker, or `speakers` + `turns` for a two-speaker dialogue; dialogue requests must not include top-level `text` or `voice`. Any field not listed, such as `output_format`, `language_code` or `temperature`, returns 400. operationId: submit_google_gemini_3_8_flash_text_to_speech requestBody: required: true content: application/json: schema: type: object required: - model - input properties: model: type: string description: Model ID. Use `google/gemini-3.8-flash/text-to-speech`. example: google/gemini-3.8-flash/text-to-speech callback_url: type: string format: uri nullable: true description: >- Optional public HTTP(S) endpoint that receives a POST when the task becomes `finished` or `failed`. HTTPS is recommended. Omit it, or send `null` or an empty string, to disable callbacks. example: https://your-domain.com/callback input: type: object properties: text: type: string minLength: 1 example: Welcome to the city museum. The east wing opens at ten. description: >- Single speaker: the text to speak. Required in single-speaker mode, not blank. Must be omitted in dialogue mode. voice: type: string enum: - Achernar - Achird - Algenib - Algieba - Alnilam - Aoede - Autonoe - Callirrhoe - Charon - Despina - Enceladus - Erinome - Fenrir - Gacrux - Iapetus - Kore - Laomedeia - Leda - Orus - Pulcherrima - Puck - Rasalgethi - Sadachbia - Sadaltager - Schedar - Sulafat - Umbriel - Vindemiatrix - Zephyr - Zubenelgenubi default: Kore description: >- Single speaker: preset voice. Must be omitted in dialogue mode. speakers: type: array items: type: object required: - speaker_id - voice properties: speaker_id: type: string minLength: 1 example: host description: >- Speaker alias referenced by `turns`. Non-empty and unique. voice: type: string enum: - Achernar - Achird - Algenib - Algieba - Alnilam - Aoede - Autonoe - Callirrhoe - Charon - Despina - Enceladus - Erinome - Fenrir - Gacrux - Iapetus - Kore - Laomedeia - Leda - Orus - Pulcherrima - Puck - Rasalgethi - Sadachbia - Sadaltager - Schedar - Sulafat - Umbriel - Vindemiatrix - Zephyr - Zubenelgenubi description: Preset voice for this speaker. additionalProperties: false description: One speaker. minItems: 2 maxItems: 2 description: >- Dialogue: exactly two speakers. Each object has only `speaker_id` and `voice`. turns: type: array items: type: object required: - speaker_id - text properties: speaker_id: type: string example: host description: Must match a `speaker_id` in `speakers`. text: type: string minLength: 1 description: What the speaker says. Not blank. style_instructions: type: string description: >- Optional delivery direction for this line only, such as `laughing` or `whispering`. additionalProperties: false description: One line of dialogue. minItems: 1 description: >- Dialogue: the lines in speaking order. At least one turn. style_instructions: type: string description: >- Optional global direction for tone, pace, accent or emotion, such as `Calm, warm documentary narration`. Applies in both modes. enable_safety_checker: type: boolean default: true description: Run the upstream safety checker. additionalProperties: false description: >- Generation parameters. Send `text` (single speaker) or `speakers` + `turns` (two-speaker dialogue), not both. examples: single_speaker: summary: Single-speaker narration with style value: model: google/gemini-3.8-flash/text-to-speech input: text: >- In the spring of 1912, the ship left Southampton carrying more than two thousand people. voice: Charon style_instructions: >- Slow, measured documentary narration with a hint of gravity dialogue: summary: Two-speaker podcast dialogue value: model: google/gemini-3.8-flash/text-to-speech callback_url: https://your-domain.com/callback input: speakers: - speaker_id: host voice: Kore - speaker_id: guest voice: Puck turns: - speaker_id: host text: >- So you really spent a winter alone at the research station? - speaker_id: guest text: Four months. The quiet was the hardest part. style_instructions: thoughtful, a little wistful - speaker_id: host text: I can't imagine. What did you miss most? style_instructions: curious responses: '200': description: Task submitted content: application/json: schema: type: object required: - code - data properties: code: type: integer enum: - 200 description: HTTP status code. data: type: object required: - task_id - status - created_time properties: task_id: type: string description: >- Task ID. Use it with [Query Task Status](/api-manual/task-management/status). status: type: string enum: - not_started description: Initial task status. created_time: type: string format: date-time description: Time the task was created (ISO 8601). example: code: 200 data: task_id: task-unified-1762160000-abc123 status: not_started created_time: '2026-11-03T10:30:00' '400': description: >- Invalid input, unsupported field, inaccessible media, or insufficient credits content: application/json: schema: type: object required: - detail properties: detail: oneOf: - type: string - type: object additionalProperties: true - type: array items: {} description: Error message. '401': description: Invalid credentials content: application/json: schema: type: object required: - detail properties: detail: oneOf: - type: string - type: object additionalProperties: true - type: array items: {} description: Error message. '403': description: Access denied content: application/json: schema: type: object required: - detail properties: detail: oneOf: - type: string - type: object additionalProperties: true - type: array items: {} description: Error message. '404': description: Unknown or disabled model content: application/json: schema: type: object required: - detail properties: detail: oneOf: - type: string - type: object additionalProperties: true - type: array items: {} description: Error message. '408': description: Request timed out content: text/plain: schema: type: string example: Request timeout '422': description: Invalid JSON or non-object request body content: application/json: schema: type: object required: - detail properties: detail: oneOf: - type: string - type: object additionalProperties: true - type: array items: {} description: Error message. '429': description: Rate or API key credit limit exceeded content: application/json: schema: type: object required: - detail properties: detail: oneOf: - type: string - type: object additionalProperties: true - type: array items: {} description: Error message. '500': description: Internal error content: application/json: schema: type: object required: - detail properties: detail: oneOf: - type: string - type: object additionalProperties: true - type: array items: {} description: Error message. '502': description: Unable to create the upstream generation task content: application/json: schema: type: object required: - detail properties: detail: oneOf: - type: string - type: object additionalProperties: true - type: array items: {} description: Error message. '503': description: The requested model is temporarily unavailable content: application/json: schema: type: object required: - detail properties: detail: oneOf: - type: string - type: object additionalProperties: true - type: array items: {} description: Error message. components: securitySchemes: BearerAuth: type: http scheme: bearer bearerFormat: API Key description: >- All API endpoints require Bearer Token authentication Get your API Key: Go to **Dashboard → API Key** ([API Key Management Page](https://vidgo.ai/apis/dashboard/api-key)) to get your API Key Add it to the request header: ``` Authorization: Bearer VIDGO_API_KEY ``` ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.