实时更改 AVSpeechUtterance 速率答案

【问题标题】：Change AVSpeechUtterance rate in real time实时更改 AVSpeechUtterance 速率
【发布时间】：2020-05-14 20:23:26
【问题描述】：

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

我想要做的是，当合成器在说话时，可以改变发声率，并通过滑块改变说话的速度。

我在滑块的 IBAction 中这样做： self.utterance = sender.value

但合成器不会改变速度。我一直在寻找信息，但我还没有找到任何东西。我能做什么？提前致谢。

【问题讨论】：

Docs 实际上说：/* 在语音话语已入队后设置这些值将无效。 */ open var rate: Float

标签： ios xcode avfoundation avspeechsynthesizer avspeechutterance

【解决方案1】：

好的，所以在玩了一些我不知道的很酷的功能之后，我找到了一种改变说话速度的方法。主要问题是话语当前被合成器排队，rate 无法更改。对应文档：

/* 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过的字符串为他提供新的话语。

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
    }
}

实现AVSpeechSynthesizerDelegate的委托方法willSpeakRangeOfSpeechString，并将合成器的委托定义为self：synthesizer.delegate = self
在该委托方法中，保存接下来要说的 characterRange。
将 IBAction func sl(_ sender: UISlider) 绑定到滑块的事件 touchUpInside。
在那个 IBAction 中，停止说话，并从索引中获取当前正在说话的文本的子字符串，它会继续。
构建新的话语并开始说出它
利润。

【讨论】：

【解决方案2】：

斯威夫特 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)
    }
}

【讨论】：