> ## Documentation Index
> Fetch the complete documentation index at: https://docs.gravitex.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Audio

> OpenAI-compatible audio and Gemini native TTS

## Introduction

GravitexAI audio APIs fall into two groups:

* **OpenAI format**: `/v1/audio/speech` (TTS), `/v1/audio/transcriptions` (STT), `/v1/audio/translations` — compatible with the OpenAI Audio API.
* **Gemini native format**: `POST /v1beta/models/{model}:generateContent` with `responseModalities: ["AUDIO"]` and `speechConfig` (e.g. `gemini-2.5-flash-preview-tts`).

Base URL: `https://api.gravitex.ai`. For Gemini auth, see [Gemini native format](/en/api-reference/endpoint/gemini-native).

## Authentication

<ParamField header="Authorization" type="string" required>
  Bearer Token, e.g. `Bearer sk-xxxxxxxxxx` (OpenAI and Gemini)
</ParamField>

<ParamField header="x-goog-api-key" type="string">
  Optional for Gemini: `x-goog-api-key: sk-xxxxxxxxxx`
</ParamField>

## Request examples

<Tabs>
  <Tab title="OpenAI format">
    <Tabs>
      <Tab title="Text-to-speech">
        **POST** `/v1/audio/speech`

        ```bash theme={null}
        curl -X POST "https://api.gravitex.ai/v1/audio/speech" \
          -H "Authorization: Bearer sk-xxxxxxxxxx" \
          -H "Content-Type: application/json" \
          -d '{
            "model": "tts-1",
            "input": "Hello from GravitexAI.",
            "voice": "alloy",
            "response_format": "mp3"
          }' \
          --output speech.mp3
        ```
      </Tab>

      <Tab title="Transcription">
        **POST** `/v1/audio/transcriptions`

        ```bash theme={null}
        curl -X POST "https://api.gravitex.ai/v1/audio/transcriptions" \
          -H "Authorization: Bearer sk-xxxxxxxxxx" \
          -F file="@audio.mp3" \
          -F model="whisper-1"
        ```
      </Tab>

      <Tab title="Translation">
        **POST** `/v1/audio/translations`

        ```bash theme={null}
        curl -X POST "https://api.gravitex.ai/v1/audio/translations" \
          -H "Authorization: Bearer sk-xxxxxxxxxx" \
          -F file="@audio.mp3" \
          -F model="whisper-1"
        ```
      </Tab>
    </Tabs>
  </Tab>

  <Tab title="Gemini format">
    **POST** `/v1beta/models/{model}:generateContent`

    Replace `{model}` with a TTS model ID and set audio output in `generationConfig`.

    ```bash theme={null}
    curl -X POST "https://api.gravitex.ai/v1beta/models/gemini-2.5-flash-preview-tts:generateContent" \
      -H "Authorization: Bearer sk-xxxxxxxxxx" \
      -H "Content-Type: application/json" \
      -d '{
        "contents": [
          {
            "parts": [
              {"text": "Say cheerfully: Have a wonderful day!"}
            ]
          }
        ],
        "generationConfig": {
          "responseModalities": ["AUDIO"],
          "speechConfig": {
            "voiceConfig": {
              "prebuiltVoiceConfig": {
                "voiceName": "Kore"
              }
            }
          }
        }
      }'
    ```

    Audio is returned in `candidates[0].content.parts[0].inlineData` (Base64, often PCM):

    ```bash theme={null}
    echo "<base64_data>" | base64 --decode > out.pcm
    ```

    For multi-speaker setups, use `speechConfig.multiSpeakerVoiceConfig` — see [Google speech generation](https://ai.google.dev/gemini-api/docs/speech-generation).
  </Tab>
</Tabs>

## Common parameters

### OpenAI format

**Speech**

* **model**: e.g. `tts-1`, `tts-1-hd`
* **input**: Text to speak (max 4096 chars)
* **voice**: `alloy`, `echo`, `fable`, `onyx`, `nova`, `shimmer`

**Transcriptions / translations**

* **file**: Audio file (multipart)
* **model**: e.g. `whisper-1`

### Gemini format (TTS)

* **model** (path): e.g. `gemini-2.5-flash-preview-tts`, `gemini-2.5-pro-preview-tts`
* **contents\[].parts\[].text**: Text or style instructions
* **generationConfig.responseModalities**: must include `"AUDIO"`
* **generationConfig.speechConfig.voiceConfig.prebuiltVoiceConfig.voiceName**: e.g. `Kore`, `Puck`, `Charon`

<Note>
  Gemini audio is produced only via `generateContent`, not `/v1/audio/*`. See [Gemini native format](/en/api-reference/endpoint/gemini-native) for full parameters.
</Note>

* [OpenAI Audio API](https://platform.openai.com/docs/api-reference/audio)
* [Gemini speech generation](https://ai.google.dev/gemini-api/docs/speech-generation)