React Native TTS

React Native TTS is a text-to-speech library for React Native on iOS and Android.

Documentation

• Install
• Usage
• License
• Example project

Install

npm install --save react-native-tts
react-native link react-native-tts

Usage

Imports

import Tts from 'react-native-tts';

Speaking

Add utterance to TTS queue and start speaking. Returns promise with utteranceId.

Tts.speak('Hello, world!');

Additionally, speak() allows to pass platform-specific options 'voiceId' on IOS and 'params' on Android to underlying platform API:

Tts.speak('Hello, world!', { iosVoiceId: 'com.apple.ttsbundle.Moira-compact' });
Tts.speak('Hello, world!', { androidParams: { KEY_PARAM_PAN: -1, KEY_PARAM_VOLUME: 0.5, KEY_PARAM_STREAM: 'STREAM_MUSIC' } });

For more detail on androidParams properties, please take a look at official android documentation. Please note that there are still unsupported key with this wrapper library such as KEY_PARAM_SESSION_ID. The following are brief summarization of currently implemented keys:

• KEY_PARAM_PAN ranges from -1 to +1.

• KEY_PARAM_VOLUME ranges from 0 to 1, where 0 means silence. Note that 1 is a default value for Android.

• For KEY_PARAM_STREAM property, you can currently use one of STREAM_ALARM, STREAM_DTMF, STREAM_MUSIC, STREAM_NOTIFICATION, STREAM_RING, STREAM_SYSTEM, STREAM_VOICE_CALL,

Stop speaking and flush the TTS queue.

Tts.stop();

Waiting for initialization

On some platforms it could take some time to initialize TTS engine, and Tts.speak() will fail to speak until the engine is ready.

To wait for successfull initialization you could use getInitStatus() call.

Tts.getInitStatus().then(() => {
  Tts.speak('Hello, world!');
});

Ducking

Enable lowering other applications output level while speaking (also referred to as "ducking").

Tts.setDucking(true);

List Voices

Returns list of available voices

(not supported on Android API Level < 21, returns empty list)

Tts.voices().then(voices => console.log(voices));

// Prints:
//
// [ { id: 'com.apple.ttsbundle.Moira-compact', name: 'Moira', language: 'en-IE', quality: 300 },
// ...
// { id: 'com.apple.ttsbundle.Samantha-compact', name: 'Samantha', language: 'en-US' } ]

Voice field	Description
id	Unique voice identifier (e.g. com.apple.ttsbundle.Moira-compact)
name	Name of the voice (iOS only)
language	BCP-47 language code (e.g. 'en-US')
quality	Voice quality (300 = normal, 500 = enhanced/very high)
latency	Expected synthesizer latency (100 = very low, 500 = very high) (Android only)
networkConnectionRequired	True when the voice requires an active network connection (Android only)
notInstalled	True when the voice may need to download additional data to be fully functional (Android only)

Set default Language

Tts.setDefaultLanguage('en-IE');

Set default Voice

Sets default voice, pass one of the voiceId as reported by a call to Tts.voices()

(not available on Android API Level < 21)

Tts.setDefaultVoice('com.apple.ttsbundle.Moira-compact');

Set default Speech Rate

Sets default speech rate. The rate parameter is a float where where 0.01 is a slowest rate and 0.99 is the fastest rate.

Tts.setDefaultRate(0.6);

There is a significant difference to how the rate value is interpreted by iOS and Android native TTS APIs. To provide unified cross-platform behaviour, translation is applied to the rate value. However, if you want to turn off the translation, you can provide optional skipTransform parameter to Tts.setDefaultRate() to pass rate value unmodified.

Do not translate rate parameter:

Tts.setDefaultRate(0.6, true);

Set default Pitch

Sets default pitch. The pitch parameter is a float where where 1.0 is a normal pitch. On iOS min pitch is 0.5 and max pitch is 2.0

Tts.setDefaultPitch(1.5);

Controls the iOS silent switch behavior

Platforms: iOS

• "inherit" (default) - Use the default behavior
• "ignore" - Play audio even if the silent switch is set
• "obey" - Don't play audio if the silent switch is set

Tts.setIgnoreSilentSwitch("ignore");

Events

Subscribe to TTS events

Tts.addEventListener('tts-start', (event) => console.log("start", event));
Tts.addEventListener('tts-finish', (event) => console.log("finish", event));
Tts.addEventListener('tts-cancel', (event) => console.log("cancel", event));

Support for multiple TTS engines

Platforms: Android

Functions to list available TTS engines and set an engine to use.

Tts.engines().then(engines => console.log(engines));
Tts.setDefaultEngine('engineName');

Install (additional) language data

Shows the Android Activity to install additional language/voice data.

Tts.requestInstallData();

Troubleshooting

No text to speech engine installed on Android

On Android, it may happen that the Text-to-Speech engine is not (yet) installed on the phone. When this is the case, Tts.getInitStatus() returns an error with code no_engine. You can use the following code to request the installation of the default Google Text to Speech App. The app will need to be restarted afterwards before the changes take affect.

Tts.getInitStatus().then(() => {
  // ...
}, (err) => {
  if (err.code === 'no_engine') {
    Tts.requestInstallEngine();
  }
});

Example

There is an example project which shows use of react-native-tts on Android/iOS: https://github.com/themostaza/react-native-tts-example

License

The MIT License (MIT)

Copyright © 2016 Anton Krasovsky

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.