Inworld TTS

InworldTTS targets the Inworld TTS HTTP endpoint (POST https://api.inworld.ai/tts/v1/voice:stream). The response is NDJSON — one JSON object per line of the form {"result": {"audioContent": "<base64>", "timestampInfo": ...}} — and the provider yields the base64-decoded audio chunks as they arrive. The default model is inworld-tts-2 (sub-200 ms time-to-first-audio, 100+ languages with mid-utterance switching, natural-language voice steering). Pass model: "inworld-tts-1.5-max" to fall back to the prior generation when you need temperature control. The default audio output is PCM_S16LE @ 16 kHz so chunks drop straight into the Patter pipeline without transcoding.

Install

npm install getpatter

No vendor SDK is required — InworldTTS uses the platform fetch, so it works on Node 18+.

Authentication

The Inworld dashboard issues a Base64 token that is already in the form expected by the Authorization: Basic <token> header — paste it into INWORLD_API_KEY as-is. Do not re-encode it.If you only have the raw API key string, base64-encode `${apiKey}:` (note the trailing colon) yourself before passing it in.

export INWORLD_API_KEY="<base64-token-from-inworld-dashboard>"

Usage

// Namespaced import (pipeline mode)
import * as inworld from "getpatter/tts/inworld";

const tts = new inworld.TTS();                            // reads INWORLD_API_KEY
const tts2 = new inworld.TTS({ apiKey: "...", voice: "Olivia", language: "en" });

// Flat alias (equivalent)
import { InworldTTS } from "getpatter";

const tts3 = new InworldTTS();

# Namespaced import (pipeline mode)
from getpatter.tts import inworld

tts = inworld.TTS()                                       # reads INWORLD_API_KEY
tts = inworld.TTS(api_key="...", voice="Olivia", language="en")

# Flat alias (equivalent)
from getpatter import InworldTTS

tts = InworldTTS()

Plug it into an agent:

// npx tsx example.ts
import { Patter, Twilio, DeepgramSTT, InworldTTS } from "getpatter";

const phone = new Patter({ carrier: new Twilio(), phoneNumber: "+15550001234" });

const agent = phone.agent({
  stt: new DeepgramSTT(),                                 // DEEPGRAM_API_KEY from env
  tts: new InworldTTS({ voice: "Ashley" }),               // INWORLD_API_KEY from env
  systemPrompt: "You are a helpful assistant.",
});

await phone.serve({ agent });

import asyncio
from getpatter import Patter, Twilio, DeepgramSTT, InworldTTS

phone = Patter(carrier=Twilio(), phone_number="+15550001234")

agent = phone.agent(
    stt=DeepgramSTT(),                                    # DEEPGRAM_API_KEY from env
    tts=InworldTTS(voice="Ashley"),                       # INWORLD_API_KEY from env
    system_prompt="You are a helpful assistant.",
)

asyncio.run(phone.serve(agent))

Customising delivery mode (TTS-2)

deliveryMode controls how expressive the TTS-2 voice is. Use EXPRESSIVE for warm conversational agents, STABLE when you want consistent, predictable prosody (e.g. for IVR-style read-backs), and BALANCED for the middle ground.

import { InworldTTS } from "getpatter";

const tts = new InworldTTS({
  voice: "Ashley",
  deliveryMode: "EXPRESSIVE",                             // EXPRESSIVE | BALANCED | STABLE
  speakingRate: 1.05,                                     // 0.5–1.5
  language: "en",                                         // BCP-47
});

from getpatter import InworldTTS

tts = InworldTTS(
    voice="Ashley",
    delivery_mode="EXPRESSIVE",                           # EXPRESSIVE | BALANCED | STABLE
    speaking_rate=1.05,                                   # 0.5–1.5
    language="en",                                        # BCP-47
)

deliveryMode is TTS-2 only — it is silently ignored by the TTS-1.5 family. Conversely temperature is TTS-1.5 only and ignored by TTS-2.

Switching to TTS-1.5 for `temperature` control

When you need sampling-temperature control (e.g. for more variation across multi-turn conversations), drop down to inworld-tts-1.5-max:

import { InworldTTS } from "getpatter";

const tts = new InworldTTS({
  model: "inworld-tts-1.5-max",
  voice: "Olivia",
  temperature: 0.7,                                       // TTS-1.5 only
  language: "it",
});

from getpatter import InworldTTS

tts = InworldTTS(
    model="inworld-tts-1.5-max",
    voice="Olivia",
    temperature=0.7,                                      # TTS-1.5 only
    language="it",
)

Models

Model id	Family	Notes
`inworld-tts-2`	TTS-2 (default)	Sub-200 ms TTFA, 100+ languages, natural-language voice steering, `deliveryMode` support.
`inworld-tts-1.5-max`	TTS-1.5	Higher fidelity legacy model, `temperature` support.
`inworld-tts-1.5-mini`	TTS-1.5	Lower latency legacy model.
`inworld-tts-1-max`	TTS-1	Original generation.
`inworld-tts-1`	TTS-1	Original generation.

Options

TypeScript	Python	Default	Notes
`apiKey`	`api_key`	—	Reads `INWORLD_API_KEY` when omitted. Base64 token from the Inworld dashboard.
`model`	`model`	`"inworld-tts-2"`	One of the model ids above.
`voice`	`voice`	`"Ashley"`	Inworld voice name (e.g. `"Ashley"`, `"Olivia"`, `"Craig"`, `"Remy"`).
`language`	`language`	—	BCP-47 tag (`"en"`, `"it"`, `"es"`, …).
`audioEncoding`	`audio_encoding`	`"PCM"`	`PCM` / `LINEAR16` / `OGG_OPUS` / `MP3`.
`sampleRate`	`sample_rate`	`16000`	Hz. Pipeline default; carrier transcoding handles 8 kHz mulaw automatically.
`bitrate`	`bitrate`	`64000`	Used for `OGG_OPUS` / `MP3` encodings.
`temperature`	`temperature`	—	TTS-1.5 only. Sampling temperature.
`speakingRate`	`speaking_rate`	`1.0`	Multiplier in `[0.5, 1.5]`.
`deliveryMode`	`delivery_mode`	—	TTS-2 only. `"EXPRESSIVE"` / `"BALANCED"` / `"STABLE"`.
`baseUrl`	`base_url`	Inworld `/tts/v1/voice:stream`	Override for proxying or on-prem deployments.

Low-level usage

If you want the streaming generator without going through the pipeline-mode wrapper, instantiate the underlying provider directly with authToken as the first argument:

import { InworldTTS as LowLevelTTS } from "getpatter/providers/inworld-tts";

const tts = new LowLevelTTS("<auth-token>", {
  model: "inworld-tts-2",
  voice: "Ashley",
  sampleRate: 16000,
});

for await (const chunk of tts.synthesizeStream("Hello from the Patter pipeline.")) {
  // raw PCM_S16LE @ 16 kHz
}

Pricing

The default rate in pricing.ts is $0.020 / 1k characters for inworld-tts-2, with $0.025 / 1k for the TTS-1.5 family. These are placeholder defaults — verify against your current Inworld platform tier and override per-project via new Patter({ pricing: {...} }) if needed.

​Inworld TTS

​Install

​Authentication

​Usage

​Customising delivery mode (TTS-2)

​Switching to TTS-1.5 for temperature control

​Models

​Options

​Low-level usage

​Pricing

Inworld TTS

Install

Authentication

Usage

Customising delivery mode (TTS-2)

Switching to TTS-1.5 for `temperature` control

Models

Options

Low-level usage

Pricing