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Developer Quickstart

Make your first Realtime STT API request

In this quickstart, you'll send an audio file to the STT API and receive a transcript. It also highlights Inworld STT (inworld/inworld-stt-1), which adds Voice Profile (age, pitch, emotion, vocal style, accent) and configurable turn-taking (automatic or manual).

Make your first STT API request

Create an API key

Create an Inworld account.

In Inworld Portal, generate an API key by going to Settings > API Keys. Copy the Base64 credentials.

Set your API key as an environment variable.

macOS and Linux

export INWORLD_API_KEY='your-base64-api-key-here'

Prepare an audio file

The STT API accepts audio in several formats (e.g. MP3, OGG_OPUS, FLAC, LINEAR16). Audio bytes are sent in the request payload as a base64-encoded string — base64 is the transport encoding, not the audio format. Requirements vary by use case:

Use case	Format	Notes
File upload (sync)	LINEAR16, MP3, OGG_OPUS, FLAC, AUTO_DETECT	Sample rate can be auto-detected from file headers when possible
Streaming	LINEAR16 (PCM)	Other encodings are not supported for streaming to minimize latency and preserve quality

Recommended settings:

Sample rate: 16,000 Hz (STT performs best at this rate; lower sample rates like 8 kHz contain fewer data points, reducing accuracy)
Bit depth: 16-bit (for LINEAR16)
Channels: Mono (1 channel)

For file uploads (MP3, FLAC, OGG_OPUS, WAV), sampleRateHertz is optional — the API can auto-detect it from the file header.

Sync transcription accepts audio files up to ~16 MB. The actual duration depends on the encoding (e.g., ~18 minutes of MP3 or ~8 minutes of 16 kHz 16-bit WAV). For larger files, split them into chunks or use the WebSocket streaming endpoint.

Send the request

Audio is sent as a JSON payload with base64-encoded audio content. The API returns the complete transcript when processing is complete (and optionally Voice Profile, when returned by the API).

Create a new file inworld_stt_quickstart.py or inworld_stt_quickstart.js and use the code below. The Inworld model (inworld/inworld-stt-1) provides transcription plus optional Voice Profile (age, pitch, emotion, vocal style, accent) and configurable turn-taking for streaming.

Python

import requests
import os
import base64

# Sync endpoint
URL = "https://api.inworld.ai/stt/v1/transcribe"

# Use a 16-bit PCM WAV file (16 kHz, mono)
with open("input.wav", "rb") as f:
    audio_content = base64.b64encode(f.read()).decode("utf-8")

payload = {
    "transcribeConfig": {
        "modelId": "inworld/inworld-stt-1",
        "language": "en",
        "audioEncoding": "LINEAR16",
        "voiceProfileConfig": {
            "enableVoiceProfile": True,
        },
    },
    "audioData": {"content": audio_content},
}

headers = {
    "Authorization": f"Basic {os.getenv('INWORLD_API_KEY')}",
    "Content-Type": "application/json",
}

response = requests.post(URL, headers=headers, json=payload)
response.raise_for_status()
result = response.json()

print("Transcript:", result["transcription"]["transcript"])

# Voice Profile (when returned by the API)
if "voiceProfile" in result and result["voiceProfile"]:
    vp = result["voiceProfile"]
    if vp.get("age"):
        print("Age:", vp["age"].get("label"), vp["age"].get("confidence"))
    if vp.get("pitch"):
        print("Pitch:", vp["pitch"].get("label"), vp["pitch"].get("confidence"))

JavaScript

import fs from "fs";
import fetch from "node-fetch";

const URL = "https://api.inworld.ai/stt/v1/transcribe";
// Use a 16-bit PCM WAV file (16 kHz, mono)
const audioContent = fs.readFileSync("input.wav").toString("base64");

const payload = {
  transcribeConfig: {
    modelId: "inworld/inworld-stt-1",
    language: "en",
    audioEncoding: "LINEAR16",
    voiceProfileConfig: {
      enableVoiceProfile: true,
    }
  },
  audioData: { content: audioContent }
};

const response = await fetch(URL, {
  method: "POST",
  headers: {
    Authorization: `Basic ${process.env.INWORLD_API_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify(payload)
});

const result = await response.json();
console.log("Transcript:", result.transcription.transcript);

if (result.voiceProfile) {
  const vp = result.voiceProfile;
  if (vp.age) console.log("Age:", vp.age.label, vp.age.confidence);
  if (vp.pitch) console.log("Pitch:", vp.pitch.label, vp.pitch.confidence);
}

Review the response

The response includes the transcript and usage fields, plus optional voiceProfile when available.

Response (sync)

Field	Description
`transcription.transcript`	The transcribed text
`transcription.isFinal`	Whether the result is finalized
`transcription.wordTimestamps`	Per-word timing data (when available)
`usage`	Usage metrics for billing
`voiceProfile`	(When returned) Age, pitch, emotion, vocalStyle, accent with `label` and `confidence`

Configuration parameters

transcribeConfig

Field	Type	Required	Description
`modelId`	string	Yes	STT model ID. Use `inworld/inworld-stt-1` for WebSocket and HTTP
`language`	string	No	ISO 639 language code (e.g. `en`, `ja`). BCP-47 codes like `en-US` are also accepted and converted to the base language. If omitted, the model may auto-detect. See Language Support for the full list
`audioEncoding`	string	Yes	One of: `LINEAR16`, `MP3`, `OGG_OPUS`, `FLAC`, `AUTO_DETECT`. For streaming, use `LINEAR16` only
`sampleRateHertz`	integer	No	Sample rate in Hz. Default 16000. Can be omitted for formats with headers (MP3, FLAC, OGG_OPUS, WAV)
`numberOfChannels`	integer	No	Channel count. Default 1
`prompts`	string[]	No	Custom vocabulary / key terms (names, jargon, acronyms) that bias recognition toward those terms. A soft bias, not a hard keyword lock. Supported across models. The Realtime API names this field `prompt` (singular)
`voiceProfileConfig`	object	No	Voice Profile configuration. See below

voiceProfileConfig

Field	Type	Required	Description
`enableVoiceProfile`	bool	Yes	Set to `true` to enable Voice Profile analysis
`topN`	integer	No	Number of top labels per category to return. Default: 10

audioData

Field	Type	Required	Description
`content`	string	Yes	Base64-encoded audio bytes

Run the code

Python

pip install requests  # if needed
python inworld_stt_quickstart.py

Example output:

Transcript: Hey, I just wanted to check in on the delivery status for my order.

Streaming (WebSocket)

For real-time microphone or live audio:

First message must contain transcribeConfig (same fields as above, including voiceProfileConfig to enable Voice Profile).
Later messages send audioChunk with base64-encoded LINEAR16 (PCM) audio only.
Turn and stream end:
- To signal end of a speaker turn, send endTurn.
- Send closeStream when the client is done sending audio (required for WebSocket; gRPC clients can just close the send side).

Example first WebSocket message:

json

{
  "transcribeConfig": {
    "modelId": "inworld/inworld-stt-1",
    "audioEncoding": "LINEAR16"
  }
}

Responses stream back as Transcription (interim and final), optional voiceProfile, speech events (speechStarted when voice activity is detected, speechStopped when silence is detected after speech), and finally Usage when the stream is closed. Every server message arrives wrapped in a result envelope (errors arrive as {"error": {"code": 3, "message": "invalid transcribe config"}}):