Web Speech API

Web Speech Concepts and Usage

The Web Speech API makes web apps able to handle voice data. There are two components to this API:

• Speech recogition is accessed via the SpeechRecognition interface, which provides the ability to recognize voice context from an audio input (normally via the device's default speech recognition service) and respond appropriately. Generally you'll use the interface's constructor to create a new SpeechRecognition object, which has a number of event handlers available for detecting when speech is input through the device's microphone. The SpeechGrammar interface represents a container for a particular set of grammar that your app should recognise. Grammar is defined using JSpeech Grammar Format (JSGF.)
• Speech synthesis is accessed via the SpeechSynthesis interface, a text-to-speech component that allows programs to read out their text content (normally via the device's default speech synthesiser.) Different voice types are represented by SpeechSynthesisVoice objects, and different parts of text that you want to be spoken are represented by SpeechSynthesisUtterance objects. You can get these spoken by passing them to the SpeechSynthesis.speak() method.

For more details on using these features, see Using the Web Speech API.

Web Speech API Interfaces

Speech recognition

SpeechRecognition

The controller interface for the recognition service; this also handles the SpeechRecognitionEvent sent from the recognition service.

SpeechRecognitionAlternative

Represents a single word that has been recognised by the speech recognition service.

SpeechRecognitionError

Represents error messages from the recognition service.

SpeechRecognitionEvent

The event object for the result and nomatch events, and contains all the data associated with an interim or final speech recognition result.

SpeechGrammar

The words or patterns of words that we want the recognition service to recognize.

SpeechGrammarList

Represents a list of SpeechGrammar objects.

SpeechRecognitionResult

Represents a single recognition match, which may contain multiple SpeechRecognitionAlternative objects.

SpeechRecognitionResultList

Represents a list of SpeechRecognitionResult objects, or a single one if results are being captured in continuous mode.

Speech synthesis

SpeechSynthesis

The controller interface for the speech service; this can be used to retrieve information about the synthesis voices available on the device, start and pause speech, and other commands besides.

SpeechSynthesisErrorEvent

Contains information about any errors that occur while processing SpeechSynthesisUtterance objects in the speech service.

SpeechSynthesisEvent

Contains information about the current state of SpeechSynthesisUtterance objects that have been processed in the speech service.

SpeechSynthesisUtterance

Represents a speech request. It contains the content the speech service should read and information about how to read it (e.g. language, pitch and volume.)

SpeechSynthesisVoice

Represents a voice that the system supports. Every SpeechSynthesisVoice has its own relative speech service including information about language, name and URI.

Window.speechSynthesis

Specced out as part of a [NoInterfaceObject] interface called SpeechSynthesisGetter, and Implemented by the Window object, the speechSynthesis property provides access to the SpeechSynthesis controller, and therefore the entry point to speech synthesis functionality.

Examples

The Web Speech API repo on GitHub contains demos to illustrate speech recognition and synthesis.

Specifications

Specification	Status	Comment
Web Speech API	Draft	Initial definition

Browser compatibility

• [1] Speech recognition interfaces are currently prefixed in Chrome, so you'll need to prefix interface names appropriately, e.g. webkitSpeechRecognition; You'll also need to serve your code through a web server for recognition to work. Speech synthesis is fully supported without prefixes.
• [2] Recognition can be enabled via the media.webspeech.recognition.enable flag in about:config; synthesis is switched on by default. Note that currently only the speech synthesis part is available in Firefox Desktop — the speech recognition part will be available soon, once the required internal permissions are sorted out.

Firefox OS permissions

To use speech recognition in an app, you need to specify the following permissions in your manifest:

"permissions": {
  "audio-capture" : {
    "description" : "Audio capture"
  },
  "speech-recognition" : {
    "description" : "Speech recognition"
  }
}

You also need a privileged app, so you need to include this as well:

  "type": "privileged"

Speech synthesis needs no permissions to be set.

See also

• Using the Web Speech API
• SitePoint article
• HTML5Rocks article
• Demo [aurelio.audero.it]