# Encoding

`encoding` _string_Default: `mp3`

Text to Speech Request  Text to Speech Stream  English Only

The Encoding feature gives users the ability to specify the desired format of the resulting text-to-speech audio output.

| Encoding     | Description                                 | Availability        |
| ------------ | ------------------------------------------- | ------------------- |
| **linear16** | 16-bit, little-endian, signed PCM WAV data. | `REST` ,`Streaming` |
| **mulaw**    | Mu-law encoded WAV data.                    | `REST` ,`Streaming` |
| **alaw**     | A-law encoded WAV data.                     | `REST` ,`Streaming` |
| **mp3**      | MP3 audio compression format.               | `REST`              |
| **opus**     | Ogg Opus codec.                             | `REST`              |
| **flac**     | Free Lossless Audio Codec (FLAC).           | `REST`              |
| **aac**      | Advanced Audio Coding format.               | `REST`              |

:::callout{intent="warning"}
The streaming WebSocket emits raw audio only: `linear16` (the streaming default), `mulaw`, or `alaw`. Compressed and containerized encodings (`mp3`, `opus`, `flac`, `aac`) are available on the REST endpoint only, where `mp3` is the default.
:::

## Enable Feature

To enable Encoding, include the `encoding` parameter in the query string with the desired encoding option.

**Example**:

**`Text`**

```text Text
https://api.deepgram.com/v1/speak?encoding=linear16
```

### CURL Examples

You can use the following cURL command in a terminal or your favorite API client to synthesize text into speech with a specific encoding.

**Linear16 encoding**:

**`cURL`**

```bash cURL
curl --request POST \
     --url "https://api.deepgram.com/v1/speak?model=aura-2-thalia-en&encoding=linear16&container=wav" \
     --header "Authorization: Token DEEPGRAM_API_KEY" \
     --header 'Content-Type: application/json' \
     --data '{"text": "Hello, how can I help you today?"}' \
     --output outputfile_Linear16.wav \
     --fail-with-body \
     --silent || echo "Request failed"
```

**MP3 encoding with bitrate of 32 kbits/second**:

**`cURL`**

```bash cURL
curl --request POST \
     --url "https://api.deepgram.com/v1/speak?model=aura-2-thalia-en&encoding=mp3&bit_rate=32000" \
     --header "Authorization: Token DEEPGRAM_API_KEY" \
     --header 'Content-Type: application/json' \
     --data '{"text": "Hello, how can I help you today?"}' \
     --output outputfile_mp3_32000.mp3 \
     --fail-with-body \
     --silent || echo "Request failed"
```

:::callout{intent="warning"}
Replace `YOUR_DEEPGRAM_API_KEY` with your [Deepgram API Key](/guides/guides-docs-create-additional-api-keys).
:::

### Query Parameters

| Parameter  | Value                                                        | Type     | Description                                      |
| ---------- | ------------------------------------------------------------ | -------- | ------------------------------------------------ |
| `encoding` | `linear16` `mulaw` `alaw` `mp3`(default) `opus` `flac` `aac` | `string` | The chosen encoding format for the output audio. |

## Analyze Response

Upon successful processing of the request, you will receive an audio file containing the synthesized text-to-speech output, along with response headers providing additional information.

:::callout{intent="info"}
The audio file is streamed back to you, so you may begin playback as soon as the first byte arrives. Read the guide [Streaming Audio Outputs](/guides/results-processing-2-streaming-the-audio-output) to learn how to begin playing the stream immediately versus waiting for the entire file to arrive.
:::

### Response Headers Example

**`http`**

```text http
HTTP/1.1 200 OK
< content-type: audio/mpeg
< dg-model-name: aura-2-thalia-en
< dg-model-uuid: e4979ab0-8475-4901-9d66-0a562a4949bb
< dg-char-count: 32
< dg-request-id: bf6fc5c7-8f84-479f-b70a-602cf5bf18f3
< transfer-encoding: chunked
< date: Thu, 29 Feb 2024 19:20:48 GMT
```

:::callout{intent="info"}
To see these response headers when making a CURL request, add `-v` or `--verbose` to your request.
:::

This includes:

- `content-type`: Specifies the media type of the resource, in this case, `audio/mpeg`, indicating the format of the audio file returned.
- `dg-request-id`: A unique identifier for the request, useful for debugging and tracking purposes.
- `dg-model-uuid`: The unique identifier of the model that processed the request.
- `dg-char-count`: Indicates the number of characters that were in the input text for the text-to-speech process.
- `dg-model-name`: The name of the model used to process the request.
- `transfer-encoding`: Specifies the form of encoding used to safely transfer the payload to the recipient.
- `date`: The date and time the response was sent.

## Related pages

- [Amazon SageMaker](./amazon-sagemaker-index.md)
- [Aura](./aura-index.md)
- [Changelog](../changelog.md)
- [Custom Vocabulary](./custom-vocabulary-index.md)
- [Deepgram's Docs](../index.md)
- [Deployment](./deployment-index.md)
- [Docker/Podman](./docker-podman-index.md)
- [Features](./features-index.md)
- [Flux TTS](./flux-tts-index.md)
- [Formatting](./formatting-index.md)

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