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MODEL ID google:gemini@3.1-flash-tts
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Gemini 3.1 Flash TTS

Google
by Google

Gemini 3.1 Flash TTS is a text-to-speech model for expressive spoken audio generation from text. It supports granular control over delivery through audio tags, native multi-speaker dialogue, and speech generation across 70+ languages, making it suitable for narration, conversational voice apps, podcasts, audiobooks, and other production-oriented voice workflows.

Gemini 3.1 Flash TTS

API Options

Platform-level options for task execution and delivery.

taskType

string required value: audioInference

Identifier for the type of task being performed

taskUUID

string required UUID v4

UUID v4 identifier for tracking tasks and matching async responses. Must be unique per task.

outputType

string default: URL

Audio output type.

Allowed values 3 values

outputFormat

string default: MP3

Specifies the file format of the generated output. The available values depend on the task type and the specific model's capabilities.

  • `MP3`: Compressed audio, smaller file size.
  • `WAV`: Uncompressed, high-quality audio.
  • `FLAC`: Lossless compression.
  • `OGG`: Open-source compressed audio format (Vorbis codec).
Allowed values 4 values

audioSettings

object

Audio encoding settings for controlling the bitrate, number of channels, and sample rate of the generated audio. Only applicable for lossy output formats (MP3 and OGG). When using lossless formats (WAV or FLAC), this parameter must not be provided.

The available sample rates and valid bitrate ranges depend on the output format. For OGG, bitrate limits also vary by the number of channels.

MP3 bitrate limits

Bitrate limits for MP3 are the same regardless of mono or stereo.

Sample Rate Min Bitrate Max Bitrate
8,000 Hz 8 kbps 64 kbps
11,025 Hz 8 kbps 64 kbps
12,000 Hz 8 kbps 64 kbps
16,000 Hz 8 kbps 160 kbps
22,050 Hz 8 kbps 160 kbps
24,000 Hz 8 kbps 160 kbps
32,000 Hz 32 kbps 320 kbps
44,100 Hz 32 kbps 320 kbps
48,000 Hz 32 kbps 320 kbps
OGG bitrate limits — Mono (1 channel)
Sample Rate Min Bitrate Max Bitrate
8,000 Hz 8 kbps 40 kbps
12,000 Hz 16 kbps 48 kbps
16,000 Hz 16 kbps 96 kbps
24,000 Hz 16 kbps 80 kbps
48,000 Hz 32 kbps 224 kbps
OGG bitrate limits — Stereo (2 channels)
Sample Rate Min Bitrate Max Bitrate
8,000 Hz 16 kbps 80 kbps
12,000 Hz 16 kbps 96 kbps
16,000 Hz 24 kbps 192 kbps
24,000 Hz 32 kbps 160 kbps
48,000 Hz 48 kbps 256 kbps

Lossless formats: When outputFormat is set to WAV or FLAC, the audioSettings parameter is not available since these formats produce uncompressed or lossless audio with no configurable encoding settings.

Properties 3 properties
audioSettings » bitrate

bitrate

integer min: 8

Audio bitrate in kbps.

audioSettings » channels

channels

integer default: 2

Number of audio channels. 1 for mono, 2 for stereo.

Allowed values 2 values
audioSettings » sampleRate

sampleRate

integer

Audio sample rate in Hz.

webhookURL

string URI

Specifies a webhook URL where JSON responses will be sent via HTTP POST when generation tasks complete. For batch requests with multiple results, each completed item triggers a separate webhook call as it becomes available.

Learn more 1 resource

deliveryMethod

string default: sync

Determines how the API delivers task results.

Allowed values 2 values
Returns complete results directly in the API response.
Returns an immediate acknowledgment with the task UUID. Poll for results using getResponse.
Learn more 1 resource

uploadEndpoint

string URI

Specifies a URL where the generated content will be automatically uploaded using the HTTP PUT method. The raw binary data of the media file is sent directly as the request body. For secure uploads to cloud storage, use presigned URLs that include temporary authentication credentials.

Common use cases:

  • Cloud storage: Upload directly to S3 buckets, Google Cloud Storage, or Azure Blob Storage using presigned URLs.
  • CDN integration: Upload to content delivery networks for immediate distribution. 
// S3 presigned URL for secure upload
https://your-bucket.s3.amazonaws.com/generated/content.mp4?X-Amz-Signature=abc123&X-Amz-Expires=3600

// Google Cloud Storage presigned URL
https://storage.googleapis.com/your-bucket/content.jpg?X-Goog-Signature=xyz789

// Custom storage endpoint
https://storage.example.com/uploads/generated-image.jpg

The content data will be sent as the request body to the specified URL when generation is complete.

ttl

integer min: 60

Time-to-live (TTL) in seconds for generated content. Only applies when outputType is URL.

includeCost

boolean default: false

Include task cost in the response.

numberResults

integer min: 1 max: 4 default: 1

Number of results to generate. Each result uses a different seed, producing variations of the same parameters.

Generation Parameters

Core parameters for controlling the generated content.

model

string required value: google:gemini@3.1-flash-tts

Identifier of the model to use for generation.

Learn more 3 resources

speech

object required

Settings for speech generation.

Properties 4 properties
speech » text

text

string required min: 1 max: 4000

Text to convert to speech. For dialogue mode, use speaker tags such as [Sam] Hello [Bob] Hi there. Provider markup tags like [laughs] and [short pause] are also supported.

Learn more 2 resources
speech » voice

voice

string default: Zephyr

Voice identifier to use. Set to auto for automatic selection.

Allowed values 30 values
Female, Soft
Male, Friendly
Male, Gravelly
Male, Smooth
Male, Firm
Female, Breezy
Female, Bright
Female, Easy-going
Male, Informative
Female, Smooth
Male, Breathy
Female, Clear
Male, Excitable
Female, Mature
Male, Clear
Female, Firm
Female, Upbeat
Female, Youthful
Male, Firm
Male, Upbeat
Female, Forward
Male, Informative
Male, Lively
Male, Knowledgeable
Male, Even
Female, Warm
Male, Easy-going
Female, Gentle
Female, Bright
Male, Casual
speech » voices

voices

array of objects items: 2

Two-speaker dialogue configuration. Use instead of voice for multi-speaker generation.

Properties 2 properties
speech » voices » speaker
speaker
string required min: 1

Unique alphanumeric speaker alias. Must appear in the text as [Alias].

speech » voices » voice
voice
string required default: Zephyr

Voice identifier to use. Set to auto for automatic selection.

Allowed values 30 values
Female, Soft
Male, Friendly
Male, Gravelly
Male, Smooth
Male, Firm
Female, Breezy
Female, Bright
Female, Easy-going
Male, Informative
Female, Smooth
Male, Breathy
Female, Clear
Male, Excitable
Female, Mature
Male, Clear
Female, Firm
Female, Upbeat
Female, Youthful
Male, Firm
Male, Upbeat
Female, Forward
Male, Informative
Male, Lively
Male, Knowledgeable
Male, Even
Female, Warm
Male, Easy-going
Female, Gentle
Female, Bright
Male, Casual
speech » language

language

string min: 1 default: en-US

Language code for speech generation.

Allowed values 87 values
Arabic (Egypt)
Bangla (Bangladesh)
Dutch (Netherlands)
English (India)
English (United States)
French (France)
German (Germany)
Hindi (India)
Indonesian (Indonesia)
Italian (Italy)
Japanese (Japan)
Korean (South Korea)
Marathi (India)
Polish (Poland)
Portuguese (Brazil)
Romanian (Romania)
Russian (Russia)
Spanish (Spain)
Tamil (India)
Telugu (India)
Thai (Thailand)
Turkish (Turkey)
Ukrainian (Ukraine)
Vietnamese (Vietnam)
Afrikaans (South Africa)
Albanian (Albania)
Amharic (Ethiopia)
Arabic (World)
Armenian (Armenia)
Azerbaijani (Azerbaijan)
Basque (Spain)
Belarusian (Belarus)
Bulgarian (Bulgaria)
Burmese (Myanmar)
Catalan (Spain)
Cebuano (Philippines)
Chinese, Mandarin (China)
Chinese, Mandarin (Taiwan)
Croatian (Croatia)
Czech (Czech Republic)
Danish (Denmark)
English (Australia)
English (United Kingdom)
Estonian (Estonia)
Filipino (Philippines)
Finnish (Finland)
French (Canada)
Galician (Spain)
Georgian (Georgia)
Greek (Greece)
Gujarati (India)
Haitian Creole (Haiti)
Hebrew (Israel)
Hungarian (Hungary)
Icelandic (Iceland)
Javanese (Java)
Kannada (India)
Konkani (India)
Lao (Laos)
Latin (Vatican City)
Latvian (Latvia)
Lithuanian (Lithuania)
Luxembourgish (Luxembourg)
Macedonian (North Macedonia)
Maithili (India)
Malagasy (Madagascar)
Malay (Malaysia)
Malayalam (India)
Mongolian (Mongolia)
Nepali (Nepal)
Norwegian, Bokmål (Norway)
Norwegian, Nynorsk (Norway)
Odia (India)
Pashto (Afghanistan)
Persian (Iran)
Portuguese (Portugal)
Punjabi (India)
Serbian (Serbia)
Sindhi (India)
Sinhala (Sri Lanka)
Slovak (Slovakia)
Slovenian (Slovenia)
Spanish (Latin America)
Spanish (Mexico)
Swahili (Kenya)
Swedish (Sweden)
Urdu (Pakistan)
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