OpenAI Text-to-Speech (TTS)

Introduction

The Audio API provides a speech endpoint based on OpenAI’s TTS (text-to-speech) model, enabling users to:

  • Narrate a written blog post.

  • Produce spoken audio in multiple languages.

  • Give real-time audio output using streaming.

Prerequisites

  1. Create an OpenAI account and obtain an API key. You can sign up at the OpenAI signup page and generate an API key on the API Keys page.

  2. Add the spring-ai-openai dependency to your project’s build file. For more information, refer to the Dependency Management section.

Auto-configuration

Spring AI provides Spring Boot auto-configuration for the OpenAI Text-to-Speech Client. To enable it add the following dependency to your project’s Maven pom.xml file:

<dependency>
    <groupId>org.springframework.ai</groupId>
    <artifactId>spring-ai-openai-spring-boot-starter</artifactId>
</dependency>

or to your Gradle build.gradle build file:

dependencies {
    implementation 'org.springframework.ai:spring-ai-openai-spring-boot-starter'
}
Refer to the Dependency Management section to add the Spring AI BOM to your build file.

Speech Properties

Connection Properties

The prefix spring.ai.openai is used as the property prefix that lets you connect to OpenAI.

Property

Description

Default

spring.ai.openai.base-url

The URL to connect to

api.openai.com

spring.ai.openai.api-key

The API Key

-

spring.ai.openai.organization-id

Optionally you can specify which organization used for an API request.

-

spring.ai.openai.project-id

Optionally, you can specify which project is used for an API request.

-
For users that belong to multiple organizations (or are accessing their projects through their legacy user API key), optionally, you can specify which organization and project is used for an API request. Usage from these API requests will count as usage for the specified organization and project.

Configuration Properties

The prefix spring.ai.openai.audio.speech is used as the property prefix that lets you configure the OpenAI Text-to-Speech client.

Property Description Default

spring.ai.openai.audio.speech.base-url

The URL to connect to

api.openai.com

spring.ai.openai.audio.speech.api-key

The API Key

-

spring.ai.openai.audio.speech.organization-id

Optionally you can specify which organization used for an API request.

-

spring.ai.openai.audio.speech.project-id

Optionally, you can specify which project is used for an API request.

-

spring.ai.openai.audio.speech.options.model

ID of the model to use. Only tts-1 is currently available.

tts-1

spring.ai.openai.audio.speech.options.voice

The voice to use for the TTS output. Available options are: alloy, echo, fable, onyx, nova, and shimmer.

alloy

spring.ai.openai.audio.speech.options.response-format

The format of the audio output. Supported formats are mp3, opus, aac, flac, wav, and pcm.

mp3

spring.ai.openai.audio.speech.options.speed

The speed of the voice synthesis. The acceptable range is from 0.25 (slowest) to 4.0 (fastest).

1.0
You can override the common spring.ai.openai.base-url, spring.ai.openai.api-key, spring.ai.openai.organization-id and spring.ai.openai.project-id properties. The spring.ai.openai.audio.speech.base-url, spring.ai.openai.audio.speech.api-key, spring.ai.openai.audio.speech.organization-id and spring.ai.openai.audio.speech.project-id properties if set take precedence over the common properties. This is useful if you want to use different OpenAI accounts for different models and different model endpoints.
All properties prefixed with spring.ai.openai.image.options can be overridden at runtime.

Runtime Options

The OpenAiAudioSpeechOptions class provides the options to use when making a text-to-speech request. On start-up, the options specified by spring.ai.openai.audio.speech are used but you can override these at runtime.

For example:

OpenAiAudioSpeechOptions speechOptions = OpenAiAudioSpeechOptions.builder()
    .withModel("tts-1")
    .withVoice(OpenAiAudioApi.SpeechRequest.Voice.ALLOY)
    .withResponseFormat(OpenAiAudioApi.SpeechRequest.AudioResponseFormat.MP3)
    .withSpeed(1.0f)
    .build();

SpeechPrompt speechPrompt = new SpeechPrompt("Hello, this is a text-to-speech example.", speechOptions);
SpeechResponse response = openAiAudioSpeechModel.call(speechPrompt);

Manual Configuration

Add the spring-ai-openai dependency to your project’s Maven pom.xml file:

<dependency>
    <groupId>org.springframework.ai</groupId>
    <artifactId>spring-ai-openai</artifactId>
</dependency>

or to your Gradle build.gradle build file:

dependencies {
    implementation 'org.springframework.ai:spring-ai-openai'
}
Refer to the Dependency Management section to add the Spring AI BOM to your build file.

Next, create an OpenAiAudioSpeechModel:

var openAiAudioApi = new OpenAiAudioApi(System.getenv("OPENAI_API_KEY"));

var openAiAudioSpeechModel = new OpenAiAudioSpeechModel(openAiAudioApi);

var speechOptions = OpenAiAudioSpeechOptions.builder()
    .withResponseFormat(OpenAiAudioApi.SpeechRequest.AudioResponseFormat.MP3)
    .withSpeed(1.0f)
    .withModel(OpenAiAudioApi.TtsModel.TTS_1.value)
    .build();

var speechPrompt = new SpeechPrompt("Hello, this is a text-to-speech example.", speechOptions);
SpeechResponse response = openAiAudioSpeechModel.call(speechPrompt);

// Accessing metadata (rate limit info)
OpenAiAudioSpeechResponseMetadata metadata = response.getMetadata();

byte[] responseAsBytes = response.getResult().getOutput();

Streaming Real-time Audio

The Speech API provides support for real-time audio streaming using chunk transfer encoding. This means that the audio is able to be played before the full file has been generated and made accessible.

var openAiAudioApi = new OpenAiAudioApi(System.getenv("OPENAI_API_KEY"));

var openAiAudioSpeechModel = new OpenAiAudioSpeechModel(openAiAudioApi);

OpenAiAudioSpeechOptions speechOptions = OpenAiAudioSpeechOptions.builder()
    .withVoice(OpenAiAudioApi.SpeechRequest.Voice.ALLOY)
    .withSpeed(1.0f)
    .withResponseFormat(OpenAiAudioApi.SpeechRequest.AudioResponseFormat.MP3)
    .withModel(OpenAiAudioApi.TtsModel.TTS_1.value)
    .build();

SpeechPrompt speechPrompt = new SpeechPrompt("Today is a wonderful day to build something people love!", speechOptions);

Flux<SpeechResponse> responseStream = openAiAudioSpeechModel.stream(speechPrompt);

Example Code