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MODEL ID inworld:tts@1.5-max
api-only

Inworld TTS-1.5 Max

Inworld AI
by Inworld AI

Inworld TTS-1.5 Max is a high-fidelity text-to-speech model engineered for expressive voice synthesis with rich prosody, nuanced emotional range, and broadcast-ready audio quality. It supports a wide set of languages and delivers more natural pronunciation and expressive variation suitable for narration, content creation, and immersive character voices. The Max variant prioritizes audio quality and expressiveness while still supporting responsive generation.

Inworld TTS-1.5 Max

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

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.

Core Parameters

Primary parameters that define the task output.

audioSettings

object

Advanced settings for audio generation.

Properties 3 properties
audioSettings » bitrate

bitrate

integer min: 1

Target audio bitrate in kbps. Constraints depend on the output format.

audioSettings » channels

channels

integer default: 2

Number of audio channels in the generated output (1 for Mono, 2 for Stereo).

Allowed values 2 values
audioSettings » sampleRate

sampleRate

integer min: 1000

Audio sample rate in Hz.

model

string required value: inworld:tts@1.5-max

Identifier of the model to use for generation.

speech

object required

Settings for speech generation.

Properties 3 properties
speech » text

text

string required min: 2 max: 2000

Text to convert to speech.

speech » voice

voice

string required

Voice identifier to use for speech generation.

Allowed values 73 values
speech » speed

speed

float min: 0.5 max: 1.5 step: 0.1 default: 1

Playback speed of the generated speech.

Settings

Technical parameters to fine-tune the inference process. These must be nested inside the settings object.
settings » temperature

temperature

float min: 0.1 max: 2 step: 0.01 default: 1.1

Controls randomness in generation. Lower values produce more deterministic outputs, higher values increase variation and creativity.

settings » textNormalization

textNormalization

boolean

Expands numbers, dates, abbreviations before speech generation.

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