A library that exposes device specific speech recognition capability.
This plugin contains a set of classes that make it easy to use the speech recognitioncapabilities of the underlying platform in Flutter. It supports Android, iOS, MacOS and web. Thetarget use cases for this library are commands and short phrases, not continuous spokenconversion or always on listening.
Platform Support #
| Support | Android | iOS | MacOS | Web* | Linux | Windows |
|---|---|---|---|---|---|---|
| build | ✅ | ✅ | ✅ | ✅ | ✘ | ✘ |
| speech | ✅ | ✅ | ✅ | ✅ | ✘ | ✘ |
build: means you can build and run with the plugin on that platform
speech: means most speech recognition features work. Platforms with build but not speech report false for initialize
* Only some browsers are supported, see here
Recent Updates #
6.7.0
- Now supports speech recognition on MacOS with many thanks to @alexrabin-sentracam for the PR!
- Now supports WASM compliation for web with many thanks to yeikel16 for the PR!
6.6.0 listen now uses 'SpeechListenOptions' to specify the options for the current listen session, including newoptions for controlling haptics and punctuation during recognition on iOS.
Note: Feedback from any test devices is welcome.
Using #
To recognize text from the microphone import the package and call the plugin, like so:
Minimal #
import 'package:speech_to_text/speech_to_text.dart' as stt; stt.SpeechToText speech = stt.SpeechToText(); bool available = await speech.initialize( onStatus: statusListener, onError: errorListener ); if ( available ) { speech.listen( onResult: resultListener ); } else { print("The user has denied the use of speech recognition."); } // some time later... speech.stop()Complete Flutter example #
import 'package:flutter/material.dart';import 'package:speech_to_text/speech_recognition_result.dart';import 'package:speech_to_text/speech_to_text.dart';void main() { runApp(MyApp());}class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( title: 'Flutter Demo', home: MyHomePage(), ); }}class MyHomePage extends StatefulWidget { MyHomePage({Key? key}) : super(key: key); @override _MyHomePageState createState() => _MyHomePageState();}class _MyHomePageState extends State<MyHomePage> { SpeechToText _speechToText = SpeechToText(); bool _speechEnabled = false; String _lastWords = ''; @override void initState() { super.initState(); _initSpeech(); } /// This has to happen only once per app void _initSpeech() async { _speechEnabled = await _speechToText.initialize(); setState(() {}); } /// Each time to start a speech recognition session void _startListening() async { await _speechToText.listen(onResult: _onSpeechResult); setState(() {}); } /// Manually stop the active speech recognition session /// Note that there are also timeouts that each platform enforces /// and the SpeechToText plugin supports setting timeouts on the /// listen method. void _stopListening() async { await _speechToText.stop(); setState(() {}); } /// This is the callback that the SpeechToText plugin calls when /// the platform returns recognized words. void _onSpeechResult(SpeechRecognitionResult result) { setState(() { _lastWords = result.recognizedWords; }); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar( title: Text('Speech Demo'), ), body: Center( child: Column( mainAxisAlignment: MainAxisAlignment.center, children: <Widget>[ Container( padding: EdgeInsets.all(16), child: Text( 'Recognized words:', style: TextStyle(fontSize: 20.0), ), ), Expanded( child: Container( padding: EdgeInsets.all(16), child: Text( // If listening is active show the recognized words _speechToText.isListening ? '$_lastWords' // If listening isn't active but could be tell the user // how to start it, otherwise indicate that speech // recognition is not yet ready or not supported on // the target device : _speechEnabled ? 'Tap the microphone to start listening...' : 'Speech not available', ), ), ), ], ), ), floatingActionButton: FloatingActionButton( onPressed: // If not yet listening for speech start, otherwise stop _speechToText.isNotListening ? _startListening : _stopListening, tooltip: 'Listen', child: Icon(_speechToText.isNotListening ? Icons.mic_off : Icons.mic), ), ); }}Example Apps #
In the example directory you'll find a few different example apps that demonstrate how to use theplugin.
Basic example (example/lib/main.dart)
This shows how to initialize and use the plugin and allows many of the options to be set througha simple UI. This is probably the first example to look at to understand how to use the plugin.
Provide example (example/lib/provider_example.dart)
If you are using the (Provider)[https://pub.dev/packages/provider] package in Flutter then this example shows howto use the plugin as a provider throught the SpeechToTextProvider class.
Plugin stress test (example/lib/stress.dart)
The plugin opens and closes several platform resources as it is used. To help ensure that the plugindoes not leak resources this stress test loops through various operations to make it easier totrack resource usage. This is mostly an internal development tool so not as useful for referencepurposes.
Audio player interaction (examples/audio_player_interaction/lib/main.dart)
A common use case is to have this plugin and an audio playback plugin working together. This example shows oneway to make them work well together. You can find this in
Initialize once #
The initialize method only needs to be called once per application session. After that listen,start, stop, and cancel can be used to interact with the plugin. Subsequent calls to initializeare ignored which is safe but does mean that the onStatus and onError callbacks cannot be reset afterthe first call to initialize. For that reason there should be only one instance of the plugin perapplication. The SpeechToTextProvider is one way to create a single instance and easily reuse it inmultiple widgets.
Permissions #
Applications using this plugin require user permissions.
iOS & macOS #
Add the following keys to your Info.plist file, located in <project root>/ios/Runner/Info.plist:
NSSpeechRecognitionUsageDescription- describe why your app uses speech recognition. This is called Privacy - Speech Recognition Usage Description in the visual editor.NSMicrophoneUsageDescription- describe why your app needs access to the microphone. This is called Privacy - Microphone Usage Description in the visual editor.
Additional Warning for macOS #
When running the macOS app through VSCode, the app will crash when requesting permissions. This is a known issue with Flutter https://github.com/flutter/flutter/issues/70374.
You can only request permissions if you run the app directly from Xcode.
If you are upgrading an existing MacOS app to use the new plugin don't forget to update your dependenciesand the pods by opening the project directory in your terminal and:
flutter cleanflutter pub getcd macospod installAndroid #
Add the record audio permission to your AndroidManifest.xml file, located in <project root>/android/app/src/main/AndroidManifest.xml.
android.permission.RECORD_AUDIO- this permission is required for microphone access.android.permission.INTERNET- this permission is required because speech recognition may use remote services.android.permission.BLUETOOTH- this permission is required because speech recognition can use bluetooth headsets when connected.android.permission.BLUETOOTH_ADMIN- this permission is required because speech recognition can use bluetooth headsets when connected.android.permission.BLUETOOTH_CONNECT- this permission is required because speech recognition can use bluetooth headsets when connected.
<uses-permission android:name="android.permission.RECORD_AUDIO"/> <uses-permission android:name="android.permission.INTERNET"/> <uses-permission android:name="android.permission.BLUETOOTH"/> <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/> <uses-permission android:name="android.permission.BLUETOOTH_CONNECT"/>Android SDK 30 or later
If you are targeting Android SDK, i.e. you set your targetSDKVersion to 30 or later, then you will need to add the following to your AndroidManifest.xml right after the permissions section. See the example app for the complete usage.
<queries> <intent> <action android:name="android.speech.RecognitionService" /> </intent></queries>Adding Sounds for iOS (optional) #
Android automatically plays system sounds when speech listening starts or stops but iOS does not. This plugin supports playing sounds to indicate listening status on iOS if sound files are available as assets in the application. To enable sounds in an application using this plugin add the sound files to the project and reference them in the assets section of the application pubspec.yaml. The location and filenames of the sound files must exactly match whatis shown below or they will not be found. The example application for the plugin shows the usage. Note These files should be very short as they delaythe start / end of the speech recognizer until the sound playback is complete.
assets: - assets/sounds/speech_to_text_listening.m4r - assets/sounds/speech_to_text_cancel.m4r - assets/sounds/speech_to_text_stop.m4rspeech_to_text_listening.m4r- played when the listen method is called.speech_to_text_cancel.m4r- played when the cancel method is called.speech_to_text_stop.m4r- played when the stop method is called.
Tips #
Switching Recognition Language #
The speech_to_text plugin uses the default locale for the device for speech recognition by default. However it alsosupports using any language installed on the device. To find the available languages and select a particular languageuse these properties.
There's a locales property on the SpeechToText instance that provides the list of locales installed on the deviceas LocaleName instances. Then the listen method takes an optional localeId named param which would be the localeIdproperty of any of the values returned in locales. A call looks like this:
var locales = await speech.locales(); // Some UI or other code to select a locale from the list // resulting in an index, selectedLocale var selectedLocale = locales[selectedLocale]; speech.listen( onResult: resultListener, localeId: selectedLocale.localeId, );Troubleshooting #
Speech recognition not working on iOS Simulator #
If speech recognition is not working on your simulator try going to the Settings app in the simulator:Accessibility -> Spoken content -> Voices
From there select any language and any speaker and it should download to the device. After that speechrecognition should work on the simulator.
Using a Bluetooth headset with your Mac may cause an issue with the simulator speech recognition,see: https://github.com/csdcorp/speech_to_text/issues/539 for details.
Speech recognition stops after a brief pause on Android #
Android speech recognition has a very short timeout when the speaker pauses. The duration seems to vary by deviceand version of the Android OS. In the devices I've used none have had a pause longer than 5 seconds. Unfortunatelythere appears to be no way to change that behaviour.
Android beeps on start/stop of speech recognition #
This is a feature of the Android OS and there is no supported way to disable it.
Duplicate results in browser recogntion #
On Android in Chrome and possibly other browsers, the speech API has been implemented differently. The plugin supports a fix for it butit requires a flag to be set on initialization. You can see the details in this issue
Android build #
Version 5.2.0 of the plugin and later require at least compileSdkVersion 31 for the Android build. This property can be set in the build.gradle file.
Continuous speech recognition #
There have been a number of questions about how to achieve continuous speech recognition using this plugin. Currentlythe plugin is designed for short intermittent use, like when expecting a response to a question, or issuing a singlevoice command. Issue #63 is the current home for that discussion. There is not yet a way to achieve this goal using theAndroid or iOS speech recognition capabilities.
There are at least two separate use cases for continuous speech recognition:
- voice assistant style, where recognition of a particular phrase triggers an interaction;
- dictation of text for input.
Voice assistant style interaction is possibly better handled by integrating with the existing assistant capability onthe device rather than building out a separate capability. Text dictation is available through the keyboard for standardtext input controls though there are other uses of dictation that are not currently well supported.
Browser support for speech recognition #
Web browsers vary in their level of support for speech recognition. Thisissue has some details.The best lists I've seen are https://caniuse.com/speech-recognition andhttps://developer.mozilla.org/en-US/docs/Web/API/SpeechRecognition. In particularin issue #239 it was reported that Brave Browser and Firefox for Linux do notsupport speech recognition.
Speech recognition from recorded audio #
There have been a number of questions about whether speech can be recognized from recorded audio. The short answer isthat this may be possible on iOS but doesn't appear to be on Android. There is an open issue on this here #205.
iOS interactions with other sound plugins, crash when listening or initializing, pauses #
On iOS the speech recognition plugin can interact with other sound plugins, things like WebRTC, or sound playbackor recording plugins. While this plugin tries hard to be a good citizen and properly share the various iOS soundresources there is always room for interactions. One thing that might help is to add a brief delay between the end ofanother sound plugin and starting to listen using SpeechToText. See this issuefor example.
SDK version error trying to compile for Android #
Manifest merger failed : uses-sdk:minSdkVersion 16 cannot be smaller than version 21 declared in library [:speech_to_text]The speech_to_text plugin requires at least Android SDK 21 because some of the speech functions in Androidwere only introduced in that version. To fix this error you need to change the build.gradle entry to reflectthis version. Here's what the relevant part of that file looked like as of this writing:
defaultConfig { applicationId "com.example.app" minSdkVersion 21 targetSdkVersion 28 versionCode flutterVersionCode.toInteger() versionName flutterVersionName testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner" }Recording audio on Android #
It is not currently possible to record audio on Android while doing speech recognition. The only solution right now is tostop recording while the speech recognizer is active and then start again after.
Incorrect Swift version trying to compile for iOS #
/Users/markvandergon/flutter/.pub-cache/hosted/pub.dartlang.org/speech_to_text-1.1.0/ios/Classes/SwiftSpeechToTextPlugin.swift:224:44: error: value of type 'SwiftSpeechToTextPlugin' has no member 'AVAudioSession' rememberedAudioCategory = self.AVAudioSession.Category ~~~~ ^~~~~~~~~~~~~~ /Users/markvandergon/flutter/.pub-cache/hosted/pub.dartlang.org/speech_to_text-1.1.0/ios/Classes/SwiftSpeechToTextPlugin.swift:227:63: error: type 'Int' has no member 'notifyOthersOnDeactivation' try self.audioSession.setActive(true, withFlags: .notifyOthersOnDeactivation)This happens when the Swift language version is not set correctly. See this thread for help https://github.com/csdcorp/speech_to_text/issues/45.
Swift not supported trying to compile for iOS #
`speech_to_text` does not specify a Swift version and none of the targets (`Runner`) integrating it have the `SWIFT_VERSION` attribute set.This usually happens for older projects that only support Objective-C. See this thread for help https://github.com/csdcorp/speech_to_text/issues/88.
Last word lost on Android #
There's a discussion here https://github.com/csdcorp/speech_to_text/issues/434 about this known issuewith some Android speech recognition. This issue is up to Google and other Android implementers toaddress, the plugin can't improve on their recognition quality.
Not working on a particular Android device #
The symptom for this issue is that the initialize method will always fail. If you turn on debug loggingusing the debugLogging: true flag on the initialize method you'll see 'Speech recognition unavailable'in the Android log. There's a lengthy issue discussion here https://github.com/csdcorp/speech_to_text/issues/36about this. The issue seems to be that the recognizer is not always automatically enabled on the device. Twokey things helped resolve the issue in this case at least.
Not working on an Android emulator #
The above tip about getting it working on an Android device is also useful for emulators. Some users have reported seeing another error on Android simulators - sdk gphone x86 (Pixel 3a API 30).AUDIO_RECORD perms were in Manifest, also manually set Mic perms in Android Settings. When running sample app, Initialize works, but Start failed the log looks as follows.
D/SpeechToTextPlugin(12555): put partialD/SpeechToTextPlugin(12555): put languageTagD/SpeechToTextPlugin(12555): Error 9 after start at 35 1000.0 / -100.0D/SpeechToTextPlugin(12555): Cancel listeningResolved by
Resolved it by Opening Google, clicking Mic icon and granting it perms, then everything on the App works...
First
- Go to Google Play
- Search for 'Google'
- You should find this app: https://play.google.com/store/apps/details?id=com.google.android.googlequicksearchboxIf 'Disabled' enable it
This is the SO post that helped: https://stackoverflow.com/questions/28769320/how-to-check-wether-speech-recognition-is-available-or-not
Second
Ensure the app has the required permissions. The symptom for this that you get a permanent error notification'error_audio_error` when starting a listen session. Here's a Stack Overflow post that addresses thathttps://stackoverflow.com/questions/46376193/android-speechrecognizer-audio-recording-errorHere's the important excerpt:
You should go to system setting, Apps, Google app, then enable its permission of microphone.
User reported steps
From issue #298 this is the detailed set of steps thatresolved their issue:
- install google app
- Settings > Voice > Languages - select the language
- Settings > Voice > Languages > Offline speech recognition - install language
- Settings > Language and region - select the Search language and Search region
- Delete the build folder from the root path of the project and run again
iOS recognition guidelines #
Apple has quite a good guide on the user experience for using speech, the original is herehttps://developer.apple.com/documentation/speech/sfspeechrecognizer This is the section that I think is particularly relevant:
Create a Great User Experience for Speech Recognition
Here are some tips to consider when adding speech recognition support to your app.
Be prepared to handle failures caused by speech recognition limits. Because speech recognition is a network-based service, limits are enforced so that the service can remain freely available to all apps. Individual devices may be limited in the number of recognitions that can be performed per day, and each app may be throttled globally based on the number of requests it makes per day. If a recognition request fails quickly (within a second or two of starting), check to see if the recognition service became unavailable. If it is, you may want to ask users to try again later.
Plan for a one-minute limit on audio duration. Speech recognition places a relatively high burden on battery life and network usage. To minimize this burden, the framework stops speech recognition tasks that last longer than one minute. This limit is similar to the one for keyboard-related dictation.Remind the user when your app is recording. For example, display a visual indicator and play sounds at the beginning and end of speech recognition to help users understand that they're being actively recorded. You can also display speech as it is being recognized so that users understand what your app is doing and see any mistakes made during the recognition process.
Do not perform speech recognition on private or sensitive information. Some speech is not appropriate for recognition. Don't send passwords, health or financial data, and other sensitive speech for recognition.
