AVSpeechSynthesis

AVSpeechSynthesis

API for computer synthesized speech
Users

• Announcements
• Non-sighted interfaces
• Education apps
• Many more…

AVSpeechSynthesis and Accessibility

Powerful tool for helping many users

• Cognitive
• Speech vocalization
• Non-sighted

Not a replacement for VoiceOver

• Speech can overlap with VoiceOver’s
• Won’t be available to Braille devices
• Make your app accessible instead using UIAccessibility

Create AVSpeechSynthesizer

Ensure it’s retained until speech is done
(Speech will be cancelled in the synthesizer is deallocated)

let synthesizer = AVSpeechSynthesizer()
//Create an utterance
let utterance = AVSpeechUtterance(string: contentTextView.text)
//Dispatch to synthesizer

synthesizer.speak(utterance)

AVSpeechSynthesis and Audio Sessions

//AVAudioSession automatically activated on speak()
//To mix with other audio, use
do {
    try AVAudioSession.sharedInstance().setCategory(.playback, mode:.spokenAudio, options:.mixWithOthers)
 } catch {
     print("error")
 }

//To duck other audio, use
do {
    try AVAudioSession.sharedInstance().setCategory(.playback, mode:.spokenAudio, options:.duckOthers)
} catch {
   print("error")
}

Callbacks

Delegate methods inform about the life cycle of an utterance
AVSpeechSynthesizerDelegate defines optional methods

• Speech started
• Speech finished
• Character range will be spoken
• Speech paused
• Speech continued

synthesizer.delegate = self

func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didStart utterance: AVSpeechUtterance)
{
print("Speech started")
}


func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance:
AVSpeechUtterance) {
print("Speech finished")
}

func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, willSpeakRangeOfSpeechString
characterRange: NSRange, utterance: AVSpeechUtterance) {
guard let rangeInString = Range(characterRange, in: utterance.speechString()) else { return }
print("Will speak: \(utterance.speechString[rangeInString])")
}

Choosing the Right Voice

Select with an identifier or a language
Selecting by language will select the users default voice

let utterance = AVSpeechUtterance(string: "Hello")

// Select an English (US) voice preferred by user (if no preference, default is used)
 utterance.voice = AVSpeechSynthesisVoice(language: "en-US”)

// Select the first voice

let allVoices = AVSpeechSynthesisVoice.speechVoices()

utterance.voice = AVSpeechSynthesisVoice(identifier: allVoices[0].identifier)

Languages supported

        Arabic <阿拉伯>
        Cantonese(Hong Kong)<廣東話.香港>  zh-hk
        Czech<捷克語>
        Danish <丹麥語>
        Dutch <荷蘭語>
        English (US) <英語.美國> en-us
        English (UK)<英語.英國>
        English (Australia) <英語.澳大利亞>
        English (Ireland) <英語.愛爾蘭>
        English (South Africa) <英語.南非>
        Finnish <芬蘭語>
        Flemish (Belgium) <佛蘭德.比利時>
        French(France) <法語.法國>
        French (Canada) <法語.加拿大>
        German <德語>
        Greek <希臘語>
        Hebrew <希伯來語>
        Hindi<北印度語>
        Hungarian<匈牙利語>
        Indonesian <印尼語>
        Italian <意大利語>
        Japanese <日語>
        Korean <韓國語>
        Mandarin (Mainland China) <普通話.大陸> zh-cn
        Mandarin(Taiwan) <普通話.臺灣>
        Norwegian <挪威語>
        Polish <波蘭語>
        Portuguese <葡萄牙語>
        Portuguese (Brazil) <葡萄牙語.巴西>
        Romanian <羅馬尼亞語>
        Russian <俄語>
        Slovak <斯洛伐克語>
        Spanish (Mexico) <西班牙語.墨西哥>
        Spanish (Spain) <西班牙語.西班牙>
        Swedish <瑞典語>
        Thai <泰國語>
        Turkish <土耳其語>

Speech Rate

utterance.pitchMultiplier = 1 // [0.5 - 2] Default = 1
utterance.volume = 0.25 // lower speech volume, does not affect system volume [0-1] Default = 1
utterance.rate = AVSpeechUtteranceDefaultSpeechRate // Values are pinned between AVSpeechUtteranceMinimumSpeechRate and AVSpeechUtteranceMaximumSpeechRate.

IPA Notation

Use attributed string API with IPA pronunciation


let attributedString = NSMutableAttributedString(string: "Hello iPhone") attributedString.addAttribute(.accessibilitySpeechIPANotation, value: "ˈa͡ɪ.ˈfo͡ʊn", range: NSRange(location: 6, length: 6)))


let utterance = AVSpeechUtterance(attributedString: attributedString)

Demo

Demo鏈接