texttospeechsynthesizerswift

texttospeechsynthesizerswift.swift

@objc
class TextToSpeechUtils: NSObject, AVSpeechSynthesizerDelegate {
     
    let synthesizer = AVSpeechSynthesizer()
    let audioSession = AVAudioSession.sharedInstance()
    let defaultLanguage = "en-US"
    var lastPlayingUtterance: AVSpeechUtterance?
     
    public func synthesizeSpeech(forText text: String) {
         
        if (text.isEmpty) { return }
         
        do {
            try audioSession.setCategory(AVAudioSessionCategoryPlayback, with: [.duckOthers])
            try audioSession.setActive(true)
        } catch {
            return
        }
         
        let utterance = AVSpeechUtterance(string:text)
        utterance.rate = AVSpeechUtteranceDefaultSpeechRate
        utterance.volume = 0.7
        utterance.voice = AVSpeechSynthesisVoice(language: detectLanguageFromText(text))
        self.synthesizer.speak(utterance)
         
        self.lastPlayingUtterance = utterance
    }
     
    func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance: AVSpeechUtterance) {
        if (synthesizer == self.synthesizer && self.lastPlayingUtterance == utterance) {
            do {
                // after last utterance has played - deactivate the audio session
                try self.audioSession.setActive(false);
            } catch {
                return
            }
        }
    }
     
    private func detectLanguageFromText(_ text: String) -> String {
        let tagger = NSLinguisticTagger.init(tagSchemes: [NSLinguisticTagSchemeLanguage], options: 0)
        tagger.string = text
        let textLanguage = tagger.tag(at: 0, scheme: NSLinguisticTagSchemeLanguage, tokenRange: nil, sentenceRange: nil)
        var detectedLanguage: String?
        for installedLanguage in AVSpeechSynthesisVoice.speechVoices() {
            let languageStringParts = installedLanguage.language.components(separatedBy: "-")
            if (languageStringParts.count > 0 && languageStringParts[0] == textLanguage) {
                detectedLanguage = installedLanguage.language
                break
            }
        }
         
        // if language could not be detected return default language
        return detectedLanguage ?? defaultLanguage
    }
}