This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for the proper prefixes to use in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the spec changes.
The confidence
read-only property of the SpeechRecognitionResult
interface returns a numeric estimate of how confident the speech recognition system is that the recognition is correct.
Note: Mozilla's implementation of confidence
is still being worked on — at the moment, it always seems to return 1.
Syntax
var myConfidence = speechRecognitionAlternativeInstance.confidence;
Returns
A number betwen 0 and 1.
Examples
This code is excerpted from our Speech color changer example.
recognition.onresult = function(event) { // The SpeechRecognitionEvent results property returns a SpeechRecognitionResultList object // The SpeechRecognitionResultList object contains SpeechRecognitionResult objects. // It has a getter so it can be accessed like an array // The first [0] returns the SpeechRecognitionResult at position 0. // Each SpeechRecognitionResult object contains SpeechRecognitionAlternative objects that contain individual results. // These also have getters so they can be accessed like arrays. // The second [0] returns the SpeechRecognitionAlternative at position 0. // We then return the transcript property of the SpeechRecognitionAlternative object var color = event.results[0][0].transcript; diagnostic.textContent = 'Result received: ' + color + '.'; bg.style.backgroundColor = color; console.log('Confidence: ' + event.results[0][0].confidence); }
Specifications
Specification | Status | Comment |
---|---|---|
Web Speech API The definition of 'confidence' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 33 [1] | 44 (44) [2] | Not supported | Not supported | Not supported |
Feature | Android | Chrome | Firefox Mobile (Gecko) | Firefox OS | IE Phone | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|---|
Basic support | ? | (Yes)[1] | ? | 2.5 | Not supported | Not supported | Not supported |
- [1] Speech recognition interfaces are currently prefixed on 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. - [2] Can be enabled via the
media.webspeech.recognition.enable
flag in about:config, although note that currently speech recognition won't work on Desktop Firefox — it will be properly exposed 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"