实时更改 AVSpeechUtterance 速率

Question

我目前正在开发一个iOS应用程序，使用AVSynthesizer将文本转换为语音。

我想做的是，当合成器说话时，可以更改话语速率，并使用滑块更改说话速度。

我在滑块的 IBAction 中执行此操作：self.utterance = sender.value

但是合成器不会改变速度。我一直在寻找信息，但还没有找到东西。我做什么？提前谢谢。

Answer 1

好的，所以在玩了一下我不知道的这个很酷的功能之后，我找到了一种改变话语速率的方法。主要问题是语句当前由合成器排队，无法更改rate。对应于文档：

/* Setting these values after a speech utterance has been enqueued will have no effect. */
open var rate: Float // Values are pinned between AVSpeechUtteranceMinimumSpeechRate and AVSpeechUtteranceMaximumSpeechRate.
open var pitchMultiplier: Float // [0.5 - 2] Default = 1
open var volume: Float // [0-1] Default = 1

因此，解决方法是停止合成器，并用修剪的字符串向他提供新的话语。

import UIKit
import AVFoundation
class ViewController: UIViewController {
    var synthesizer: AVSpeechSynthesizer!
    var string: String!
    var currentRange: NSRange = NSRange(location: 0, length: 0)
    @IBAction func sl(_ sender: UISlider) {
        synthesizer.stopSpeaking(at: .immediate)
        if currentRange.length > 0 {
            let startIndex = string.index(string.startIndex, offsetBy: NSMaxRange(currentRange))
            let newString = string.substring(from: startIndex)
            string = newString
            synthesizer.speak(buildUtterance(for: sender.value, with: string))
        }
    }
    func buildUtterance(for rate: Float, with str: String) -> AVSpeechUtterance {
        let utterance = AVSpeechUtterance(string: str)
        utterance.rate = rate
        utterance.voice = AVSpeechSynthesisVoice(language: "en-US")
        return utterance
    }
    override func viewDidLoad() {
        super.viewDidLoad()
        string = "I am currently developing an iOS app that converts text to speech using AVSynthesizer.What I want to do is that while the synthesizer is speaking, utterance rate can be changed and with a slider and the speed of the speaking changes. I am doing this in the IBAction of the slider: self.utterance = sender.value but the synthesizer doesn't change the speed. Ive been looking for information but I haven't found something yet. What can I do? Thanks in advance."
        synthesizer = AVSpeechSynthesizer()
        synthesizer.delegate = self
        synthesizer.speak(buildUtterance(for: AVSpeechUtteranceDefaultSpeechRate, with: string))
    }
}
extension ViewController: AVSpeechSynthesizerDelegate {
    func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, willSpeakRangeOfSpeechString characterRange: NSRange, utterance: AVSpeechUtterance) {
        debugPrint(characterRange.toRange())
        currentRange = characterRange
    }
}

1. 实现 AVSpeechSynthesizerDelegate 的委托方法willSpeakRangeOfSpeechString，并将合成器的委托定义为 self： synthesizer.delegate = self

2. 在该委托方法中，保存接下来要说出的字符范围。

3. 将IBAction func sl(_ sender: UISlider)绑定到滑块的事件 touchUpInside。

4. 在该 IBAction 中，停止说话，并从索引中获取当前正在朗读的文本的子字符串，它将继续。

5. 构建新话语并开始说出它

6. 利润。

Answer 2

swift 3

import UIKit
import AVFoundation     
class ViewController: UIViewController{
    @IBOutlet weak var sliderVolume: UISlider!  //for volume
    @IBOutlet weak var sliderRate: UISlider!    //for rate
    @IBOutlet weak var sliderPitch: UISlider!   //for pitch
    @IBOutlet weak var txtForSpeak: UITextField!
    let speechSynth = AVSpeechSynthesizer()
    @IBAction func btnStartToSpeak(_ sender: UIButton) {
        let speechUtt = AVSpeechUtterance(string: self.txtForSpeak.text!)
            speechUtt.rate = self.sliderRate.value
            speechUtt.volume = self.sliderVolume.value
            speechUtt.pitchMultiplier = self.sliderPitch.value
        self.speechSynth.speak(speechUtt)
    }
}