Audio

ARouter provides comprehensive audio support across three modes: speech-to-text (transcription and translation), text-to-speech (TTS), and audio chat (multimodal models that accept audio input and produce spoken output).

Audio Transcription

Transcribe audio files to text using the OpenAI-compatible /v1/audio/transcriptions endpoint.

curl https://api.arouter.ai/v1/audio/transcriptions \
  -H "Authorization: Bearer lr_live_xxxx" \
  -F file="@audio.mp3" \
  -F model="openai/whisper-large-v3"

Python
Node.js
cURL

from openai import OpenAI

client = OpenAI(
    base_url="https://api.arouter.ai/v1",
    api_key="lr_live_xxxx",
)

with open("audio.mp3", "rb") as audio_file:
    transcription = client.audio.transcriptions.create(
        model="openai/whisper-large-v3",
        file=audio_file,
        response_format="text",
    )

print(transcription.text)

import OpenAI from "openai";
import fs from "fs";

const client = new OpenAI({
  baseURL: "https://api.arouter.ai/v1",
  apiKey: "lr_live_xxxx",
});

const transcription = await client.audio.transcriptions.create({
  model: "openai/whisper-large-v3",
  file: fs.createReadStream("audio.mp3"),
  response_format: "text",
});

console.log(transcription.text);

curl https://api.arouter.ai/v1/audio/transcriptions \
  -H "Authorization: Bearer lr_live_xxxx" \
  -F file="@audio.mp3" \
  -F model="openai/whisper-large-v3" \
  -F response_format="text"

Transcription Parameters

Parameter	Type	Description
`file`	`file`	Audio file to transcribe. Supported formats: `flac`, `mp3`, `mp4`, `mpeg`, `mpga`, `m4a`, `ogg`, `wav`, `webm`
`model`	`string`	Model ID, e.g. `openai/whisper-large-v3`
`language`	`string`	BCP-47 language code (e.g. `"en"`, `"zh"`). Improves accuracy when specified.
`prompt`	`string`	Optional text to guide transcription style or provide vocabulary hints
`response_format`	`string`	Output format: `json` (default), `text`, `srt`, `verbose_json`, `vtt`
`temperature`	`number`	Sampling temperature 0–1. Higher values increase randomness.
`timestamp_granularities`	`string[]`	`["word"]` or `["segment"]` for timestamped output (requires `verbose_json`)

Word-Level Timestamps

transcription = client.audio.transcriptions.create(
    model="openai/whisper-large-v3",
    file=audio_file,
    response_format="verbose_json",
    timestamp_granularities=["word"],
)

for word in transcription.words:
    print(f"{word.start:.2f}s - {word.end:.2f}s: {word.word}")

Audio Translation

Translate audio from any language into English text:

Python
cURL

with open("foreign_audio.mp3", "rb") as audio_file:
    translation = client.audio.translations.create(
        model="openai/whisper-large-v3",
        file=audio_file,
        response_format="text",
    )

print(translation.text)

curl https://api.arouter.ai/v1/audio/translations \
  -H "Authorization: Bearer lr_live_xxxx" \
  -F file="@foreign_audio.mp3" \
  -F model="openai/whisper-large-v3"

Text-to-Speech

Convert text to natural-sounding speech:

Python
Node.js
cURL

response = client.audio.speech.create(
    model="openai/tts-1-hd",
    voice="nova",
    input="Hello! Welcome to ARouter, the universal AI gateway.",
)

response.stream_to_file("output.mp3")

import fs from "fs";

const response = await client.audio.speech.create({
  model: "openai/tts-1-hd",
  voice: "nova",
  input: "Hello! Welcome to ARouter, the universal AI gateway.",
});

const buffer = Buffer.from(await response.arrayBuffer());
fs.writeFileSync("output.mp3", buffer);

curl https://api.arouter.ai/v1/audio/speech \
  -H "Authorization: Bearer lr_live_xxxx" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/tts-1-hd",
    "input": "Hello! Welcome to ARouter.",
    "voice": "nova"
  }' \
  --output output.mp3

TTS Parameters

Parameter	Type	Description
`model`	`string`	TTS model, e.g. `openai/tts-1` or `openai/tts-1-hd`
`input`	`string`	Text to synthesize. Maximum 4,096 characters.
`voice`	`string`	Voice to use: `alloy`, `echo`, `fable`, `onyx`, `nova`, `shimmer`
`response_format`	`string`	Audio format: `mp3` (default), `opus`, `aac`, `flac`, `wav`, `pcm`
`speed`	`number`	Playback speed from `0.25` to `4.0` (default `1.0`)

Available Voices

Voice	Character
`alloy`	Neutral, balanced
`echo`	Softer, reflective
`fable`	Expressive, storytelling
`onyx`	Deep, authoritative
`nova`	Friendly, energetic
`shimmer`	Warm, gentle

Audio Chat (Multimodal Models)

Some models accept audio directly as a chat message input and can respond with spoken audio. Use the standard chat completions endpoint with input_audio content parts.

Audio Input

Send audio alongside text in a chat message:

{
  "model": "openai/gpt-5.4-audio-preview",
  "messages": [
    {
      "role": "user",
      "content": [
        {
          "type": "input_audio",
          "input_audio": {
            "data": "<base64-encoded-audio>",
            "format": "wav"
          }
        }
      ]
    }
  ]
}

Python
Node.js

import base64

with open("question.wav", "rb") as f:
    audio_data = base64.b64encode(f.read()).decode("utf-8")

response = client.chat.completions.create(
    model="openai/gpt-5.4-audio-preview",
    messages=[
        {
            "role": "user",
            "content": [
                {
                    "type": "input_audio",
                    "input_audio": {
                        "data": audio_data,
                        "format": "wav",
                    },
                }
            ],
        }
    ],
)

print(response.choices[0].message.content)

import fs from "fs";

const audioData = fs.readFileSync("question.wav").toString("base64");

const response = await client.chat.completions.create({
  model: "openai/gpt-5.4-audio-preview",
  messages: [
    {
      role: "user",
      content: [
        {
          type: "input_audio",
          input_audio: {
            data: audioData,
            format: "wav",
          },
        },
      ],
    },
  ],
});

console.log(response.choices[0].message.content);

Supported Input Audio Formats

Format	MIME Type
`wav`	`audio/wav`
`mp3`	`audio/mpeg`
`ogg`	`audio/ogg`
`flac`	`audio/flac`
`m4a`	`audio/m4a`
`webm`	`audio/webm`

Audio Output

Request spoken audio as part of the model response:

{
  "model": "openai/gpt-5.4-audio-preview",
  "modalities": ["text", "audio"],
  "audio": {
    "voice": "nova",
    "format": "mp3"
  },
  "messages": [{"role": "user", "content": "Tell me a short joke."}]
}

The response includes an audio field with base64-encoded audio:

{
  "choices": [
    {
      "message": {
        "role": "assistant",
        "content": null,
        "audio": {
          "id": "audio_abc123",
          "data": "<base64-encoded-mp3>",
          "expires_at": 1234567890,
          "transcript": "Why don't scientists trust atoms? Because they make up everything!"
        }
      }
    }
  ]
}

Streaming Audio Output

Audio output can be streamed for real-time playback:

with client.chat.completions.stream(
    model="openai/gpt-5.4-audio-preview",
    modalities=["text", "audio"],
    audio={"voice": "nova", "format": "pcm16"},
    messages=[{"role": "user", "content": "Tell me a short joke."}],
) as stream:
    for chunk in stream:
        delta = chunk.choices[0].delta
        if delta.audio:
            # delta.audio.data contains base64-encoded PCM chunk
            play_audio_chunk(delta.audio.data)

Supported Models

Speech-to-Text

Model	Languages	Notes
`openai/whisper-large-v3`	99+	Best accuracy
`openai/whisper-large-v3-turbo`	99+	Faster, lower cost

Text-to-Speech

Model	Quality	Latency
`openai/tts-1`	Standard	Low
`openai/tts-1-hd`	High	Medium

Audio Chat

Use GET /v1/models?output_modalities=audio to discover models supporting audio output.

Token Pricing

Audio tokens are tracked separately in usage.prompt_tokens_details:

{
  "usage": {
    "prompt_tokens": 150,
    "prompt_tokens_details": {
      "audio_tokens": 100,
      "cached_tokens": 0
    },
    "completion_tokens": 50,
    "completion_tokens_details": {
      "audio_tokens": 30
    }
  }
}

Audio tokens are priced differently from text tokens. Check usage.cost in the response for the actual charge for each request.

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Audio Transcription

Transcription Parameters

Word-Level Timestamps

Audio Translation

Text-to-Speech

TTS Parameters

Available Voices

Audio Chat (Multimodal Models)

Audio Input

Supported Input Audio Formats

Audio Output

Streaming Audio Output

Supported Models

Speech-to-Text

Text-to-Speech

Audio Chat

Token Pricing

​Audio Transcription

​Transcription Parameters

​Word-Level Timestamps

​Audio Translation

​Text-to-Speech

​TTS Parameters

​Available Voices

​Audio Chat (Multimodal Models)

​Audio Input

​Supported Input Audio Formats

​Audio Output

​Streaming Audio Output

​Supported Models

​Speech-to-Text

​Text-to-Speech

​Audio Chat

​Token Pricing

Audio Transcription

Transcription Parameters

Word-Level Timestamps

Audio Translation

Text-to-Speech

TTS Parameters

Available Voices

Audio Chat (Multimodal Models)

Audio Input

Supported Input Audio Formats

Audio Output

Streaming Audio Output

Supported Models

Speech-to-Text

Text-to-Speech

Audio Chat

Token Pricing