Cloud Text-to-Speech basics

Cloud Text-to-Speech is an API that lets you create natural-sounding, synthetic human speech as playable audio. You can use the audio data files you create using Cloud Text-to-Speech to power your applications or augment media like videos or audio recordings (in compliance with the Google Cloud Platform Terms of Service including compliance with all applicable law).

Cloud TTS converts text or Speech Synthesis Markup Language (SSML) input into audio data like MP3 or LINEAR16 (the encoding used in WAV files).

This document is a conceptual guide to using Cloud Text-to-Speech. For practical code examples, see our samples section, and see our getting started page for information on how to set up your Google Cloud project to use the Cloud Text-to-Speech API.

Basic example

Cloud TTS is ideal for any application that plays audio of human speech to users. With Cloud TTS, you can convert arbitrary strings, words, and sentences into the sound of a person speaking the same things.

Imagine that you have a voice assistant app that provides natural language feedback to your users as playable audio files. You can use Cloud TTS to have your app perform an action and then provide human speech as feedback to the user. You might want to have your app report that it successfully added an event to the user's calendar. Your app would construct a response string to report the success to the user, something like "I've added the event to your calendar."

With Cloud TTS, you can convert that response string to actual human speech to play back to the user, similar to the following example:

Example 1. Audio file generated from Cloud TTS

To create an audio file like example 1, you send a request to Cloud TTS like the following code snippet.

Note: The following sample uses the gcloud auth print-access-token command to retrieve an access token for the request. Before you run the sample, you must install and initialize the Google Cloud CLI. Replace PROJECT_ID with your project ID.

curl -H "Authorization: Bearer "$(gcloud auth print-access-token) -H "x-goog-user-project: PROJECT_ID" -H "Content-Type: application/json; charset=utf-8" --data "{
  'input':{
    'text':'With Cloud machine learning, your application interprets images, texts, and more.'
  },
  'voice':{
    'languageCode':'en-gb',
    'name':'en-GB-Chirp3-HD-Charon',
  },
  'audioConfig':{
    'audioEncoding':'LINEAR16'
  }
}" "https://texttospeech.googleapis.com/v1/text:synthesize"

Speech synthesis

The process of translating text input into audio data is called synthesis and the output of synthesis is called synthetic speech. Cloud TTS takes two types of input: raw text or SSML-formatted data (discussed below). To create a new audio file, call the synthesizeendpoint of the API.

The speech synthesis process generates raw audio data as a base64-encoded string. You must decode the base64-encoded string into an audio file before an application can play it. Most platforms and operating systems have tools for decoding base64 text into playable media files.

Note: You must decode the base64 string returned from Cloud TTS before you can play it. For more information about how to decode base64 data, see Decoding Base64-Encoded Audio Content

To learn more about synthesis, review the quickstarts or the Creating Voice Audio Files page.

Voices

Cloud TTS creates raw audio data of natural, human speech. That is, it creates audio that sounds like a person talking. When you send a synthesis request to Cloud TTS, you must specify a voice that 'speaks' the words.

Cloud TTS has a wide selection of custom voices available for you to use. The voices differ by language, gender, and accent (for some languages). For example, you can create audio that mimics the sound of a female English speaker with a British accent like the previous example. You can also convert the same text into a different voice (for example, a male English speaker with an Australian accent).

Example 2. Audio file generated with en-AU speaker

To see the complete list of the available voices, see Supported Voices.

Other audio output settings

Besides the voice, you can also configure other aspects of the audio data output created by speech synthesis. Cloud TTS supports configuring the speaking rate, pitch, volume, and sample rate hertz.

For more information, see the AudioConfig reference.

Speech Synthesis Markup Language (SSML) support

You can enhance the synthetic speech produced by Cloud TTS by marking up the text using Speech Synthesis Markup Language (SSML). SSML lets you insert pauses, acronym pronunciations, or other additional details into the audio data created by Cloud TTS. Cloud TTS supports a subset of the available SSML elements.

Note: Cloud TTS does not support all SSML elements for all available languages.

For example, you can ensure that the synthetic speech correctly pronounces ordinal numbers by providing Cloud TTS with SSML input that marks ordinal numbers as such.

Example 5. Audio file generated from plain text input

Example 6. Audio file generated from SSML input

To learn more about how to synthesize speech from SSML, see Creating Voice Audio Files.

What's next?

Get started with using Cloud Text-to-Speech by following our setup guide.