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MODEL IDinworld:tts@1.5-max
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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

stringrequiredvalue: audioInference

Identifier for the type of task being performed

taskUUID

stringrequiredUUID v4

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

outputType

stringdefault: URL

Audio output type.

Allowed values3 values

outputFormat

stringdefault: 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 values4 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 RateMin BitrateMax Bitrate
8,000 Hz8 kbps64 kbps
11,025 Hz8 kbps64 kbps
12,000 Hz8 kbps64 kbps
16,000 Hz8 kbps160 kbps
22,050 Hz8 kbps160 kbps
24,000 Hz8 kbps160 kbps
32,000 Hz32 kbps320 kbps
44,100 Hz32 kbps320 kbps
48,000 Hz32 kbps320 kbps
OGG bitrate limits — Mono (1 channel)
Sample RateMin BitrateMax Bitrate
8,000 Hz8 kbps40 kbps
12,000 Hz16 kbps48 kbps
16,000 Hz16 kbps96 kbps
24,000 Hz16 kbps80 kbps
48,000 Hz32 kbps224 kbps
OGG bitrate limits — Stereo (2 channels)
Sample RateMin BitrateMax Bitrate
8,000 Hz16 kbps80 kbps
12,000 Hz16 kbps96 kbps
16,000 Hz24 kbps192 kbps
24,000 Hz32 kbps160 kbps
48,000 Hz48 kbps256 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.

Properties3 properties
audioSettings » bitrate

bitrate

integermin: 1

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

audioSettings » sampleRate

sampleRate

integermin: 1000

Audio sample rate in Hz.

audioSettings » channels

channels

integerdefault: 2

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

Allowed values2 values

webhookURL

stringuri

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 more1 resource

deliveryMethod

stringdefault: sync

Determines how the API delivers task results.

Allowed values2 values
Returns complete results directly in the API response.
Returns an immediate acknowledgment with the task UUID. Poll for results using getResponse.
Learn more1 resource

uploadEndpoint

stringuri

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

integermin: 60

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

includeCost

boolean

Include task cost in the response.

numberResults

integermin: 1max: 4default: 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.

model

stringrequiredvalue: inworld:tts@1.5-max

Identifier of the model to use for generation.

Learn more3 resources

speech

objectrequired

Settings for speech generation.

Properties3 properties
speech » text

text

stringrequiredmin: 2max: 2000

Text to convert to speech.

speech » voice

voice

stringrequired

Voice identifier to use for speech generation.

Allowed values73 values
speech » speed

speed

floatmin: 0.5max: 1.5step: 0.1default: 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

floatmin: 0.1max: 2step: 0.01default: 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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