Encoding allows you to specify the expected encoding of your audio output.

encoding stringEnglish

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

The following encoding options are supported:

  • linear16: 16-bit, little-endian, signed PCM WAV data.
  • mulaw: Mu-law encoded WAV data.
  • alaw: A-law encoded WAV data.
  • mp3: MP3 audio compression format.
  • opus: Ogg Opus codec.
  • flac: Free Lossless Audio Codec (FLAC).
  • aac: Advanced Audio Coding format.

Enable Feature

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




If you do not specify a model, the default model aura-asteria-en will be used.

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 --request POST \
     --url "https://api.deepgram.com/v1/speak?model=aura-asteria-en&encoding=linear16" \
     --header "Authorization: Token DEEPGRAM_API_KEY" \
     --header 'Content-Type: application/json' \
     --output outputfile_Linear16.wav \
     --data '{"text": "Hello, how can I help you today?"}'\
     --fail-with-body \
     --silent \
     || (jq . outputfile_Linear16.wav && rm outputfile_Linear16.wav)

MP3 encoding with bitrate of 32 kbits/second:

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

Query Parameters

stringThe chosen encoding format for the output audio.

In addition to the encoding parameter, you can further customize the audio output using the following optional query parameters:

  • container: File format wrapper for the audio.
  • sample_rate: Sample rate of the audio output.
  • bit_rate: Bit rate of the audio output.


When using VoIP (Voice over Internet Protocol), we recommend adding container=none to your request to prevent request header information being misinterpreted as audio, which can result in static or click sounds.

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.


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 to learn how to begin playing the stream immediately versus waiting for the entire file to arrive.

Response Headers Example

HTTP/1.1 200 OK
< content-type: audio/mpeg
< dg-model-name: aura-asteria-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


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.

API Error Responses


For information on Deepgram's error messages and error codes, read the API Reference Errors page.


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