AVSpeechSynthesizer 文字转语音
  简单示例:
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   |  AVSpeechSynthesizer *synthesizer = [AVSpeechSynthesizer new]; AVSpeechUtterance * utterance = [[AVSpeechUtterance alloc] initWithString:@"需要转化的文字"];
  [synthesizer speakUtterance:utterance];
 
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指定声音:
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   |  AVSpeechSynthesisVoice *voice = [AVSpeechSynthesisVoice voiceWithLanguage:@"en-US"]; utterance.voice = voiceType;
 
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语速:
队列中插入语音
使用 https://github.com/quentinhayot/QHSpeechSynthesizerQueue