TTS(Text To Speech 文本轉語音縮寫)

簡介

涉及到AVFoundatio框架中的AVSpeechSynthesizer、AVSpeechUtterance、AVSpeechSynthesisVoice三個類，這三個類的聲明都在AVSpeechSynthesis.h里，這三個類比較簡單。

需要用到的一些枚舉與宏

• 播放暫停時是立即停止播放語音還是播放完當前詞再暫停。

  typedef NS_ENUM(NSInteger, AVSpeechBoundary) {
      AVSpeechBoundaryImmediate,
      AVSpeechBoundaryWord
  }
  

• 語音質量

  typedef NS_ENUM(NSInteger, AVSpeechSynthesisVoiceQuality) {
      AVSpeechSynthesisVoiceQualityDefault = 1,
      AVSpeechSynthesisVoiceQualityEnhanced
  }
  

• 速率

  AVF_EXPORT const float AVSpeechUtteranceMinimumSpeechRate NS_AVAILABLE_IOS(7_0);
  AVF_EXPORT const float AVSpeechUtteranceMaximumSpeechRate NS_AVAILABLE_IOS(7_0);
  AVF_EXPORT const float AVSpeechUtteranceDefaultSpeechRate NS_AVAILABLE_IOS(7_0);
  

• 注意：設置屬性字符串時，AVSpeechSynthesisIPANotationAttribute的正確使用，最后會有Demo傳送門

  AVF_EXPORT NSString *const AVSpeechSynthesisIPANotationAttribute;
  

AVSpeechUtterance

要開始說話，請指定AVSpeechSynthesisVoice和要說出的字符串，然后根據需要隨意更改速率，音高或音量。

四種初始化方法

+ (instancetype)speechUtteranceWithString:(NSString *)string;
+ (instancetype)speechUtteranceWithAttributedString:(NSAttributedString *)string API_AVAILABLE(ios(10.0), watchos(3.0), tvos(10.0));

- (instancetype)initWithString:(NSString *)string;
- (instancetype)initWithAttributedString:(NSAttributedString *)string API_AVAILABLE(ios(10.0), watchos(3.0), tvos(10.0));

通過以上創建出來的實例，其語音、語速、音調、音量都是默認的，可以通過屬性進行定制，但是在入隊后設置這些值將不起作用。其中rate的值應該介于AVSpeechUtteranceMinimumSpeechRate和AVSpeechUtteranceMaximumSpeechRate之間

@property(nonatomic, retain, nullable) AVSpeechSynthesisVoice *voice;
@property(nonatomic) float rate;           
@property(nonatomic) float pitchMultiplier;  // [0.5 - 2] Default = 1
@property(nonatomic) float volume;           // [0-1] Default = 1
@property(nonatomic) NSTimeInterval preUtteranceDelay;    // Default is 0.0
@property(nonatomic) NSTimeInterval postUtteranceDelay;   // Default is 0.0

有兩個屬性可以獲得當前播放的字符串或屬性字符串

@property(nonatomic, readonly) NSString *speechString;
@property(nonatomic, readonly) NSAttributedString *attributedSpeechString

AVSpeechSynthesisVoice

通過指定應該在其中說出文本的語言代碼來檢索語音，或者通過使用voiceWithIdentifier來獲取已知語音標識符。

現支持的語音語言37種,可以用類方法speechVoices獲取

+ (NSArray<AVSpeechSynthesisVoice *> *)speechVoices;

獲取設備當前語言語音碼

+ (NSString *)currentLanguageCode;

根據指定的語言語音碼獲取語音

+ (nullable AVSpeechSynthesisVoice *)voiceWithLanguage:(nullable NSString *)languageCode;

根據指定的語言語音標識碼獲取語音 iOS9.0之后可用

+ (nullable AVSpeechSynthesisVoice *)voiceWithIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(9_0);

獲取某個語音的信息，只讀

@property(nonatomic, readonly) NSString *language;
@property(nonatomic, readonly) NSString *identifier NS_AVAILABLE_IOS(9_0);
@property(nonatomic, readonly) NSString *name NS_AVAILABLE_IOS(9_0);
@property(nonatomic, readonly) AVSpeechSynthesisVoiceQuality quality NS_AVAILABLE_IOS(9_0);

AVSpeechSynthesizer

合成器

是否正在播放、暫停

@property(nonatomic, readonly, getter=isSpeaking) BOOL speaking;
@property(nonatomic, readonly, getter=isPaused) BOOL paused;

將已加入或正在講話的相同AVSpeechUtterance加入會引發異常。

- (void)speakUtterance:(AVSpeechUtterance *)utterance;

以下方法只對正在講話的語音進行操作才有效。 如果成功則返回YES，失敗則返回NO。

- (BOOL)stopSpeakingAtBoundary:(AVSpeechBoundary)boundary;
- (BOOL)pauseSpeakingAtBoundary:(AVSpeechBoundary)boundary;
- (BOOL)continueSpeaking;

指定要用于合成語音的音頻通道，如AVAudioSession當前路徑中的通道描述所述。
語音音頻將復制到每個指定的頻道。默認值為nil，表示系統默認值。

@property(nonatomic, retain, nullable) NSArray<AVAudioSessionChannelDescription *> *outputChannels;

學習資源

#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>

@interface ViewController ()

@property(nonatomic, strong) AVSpeechSynthesizer *speechSynthesizer;
@property(nonatomic, strong) AVSpeechUtterance *utterance;
@property(nonatomic, strong) UILabel *label;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.speechSynthesizer = [[AVSpeechSynthesizer alloc] init];
    [self commonInit];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)commonInit {
    UISwitch *senderSwitch = [[UISwitch alloc] init];
    senderSwitch.on = YES;
    senderSwitch.frame = CGRectMake(0, 0, 100, 20);
    senderSwitch.center = self.view.center;
    [senderSwitch addTarget:self action:@selector(updateUtterance:) forControlEvents:UIControlEventValueChanged];
    [self.view addSubview:senderSwitch];
    
    self.label = [[UILabel alloc] initWithFrame:CGRectMake((self.view.bounds.size.width - 200)/2.0f, CGRectGetMaxY(senderSwitch.frame) - 80, 200, 20)];
    self.label.textAlignment = NSTextAlignmentCenter;
    [self.view addSubview:self.label];
    
    UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
    btn.frame = CGRectMake((self.view.bounds.size.width - 128)/2.0f, CGRectGetMaxY(senderSwitch.frame) + 20, 128, 128);
    [btn setImage:[UIImage imageNamed:@"audio"] forState:UIControlStateNormal];
    [btn addTarget:self action:@selector(btnClick:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn];
    
    [self updateUtterance:senderSwitch];
}

- (void)updateUtterance:(UISwitch *)sender {
    sender.on = !sender.isOn;
    if (sender.on) {
        NSMutableAttributedString *attString = [[NSMutableAttributedString alloc] initWithString:@"Tsutsumi"];
        // 這里的國際音標可以隨意修改 eg:"t?n.t?n.m?"  "t?n.m?" ... 可以多試試其他的情況
        [attString addAttribute:AVSpeechSynthesisIPANotationAttribute value:@"t?n.t?n.mi" range:NSMakeRange(0, attString.length)];
        self.utterance = [AVSpeechUtterance speechUtteranceWithAttributedString:attString];
        
        self.label.text = @"Tsutsumi(Attributed)";
    } else {
        self.utterance = [AVSpeechUtterance speechUtteranceWithString:@"Tsutsumi"];
        self.label.text = @"Tsutsumi";
    }
}

- (void)btnClick:(UIButton *)sender {
    if (self.speechSynthesizer.isSpeaking) {
        NSLog(@"正在朗讀中....");
        return;
    }
    [self.speechSynthesizer speakUtterance:self.utterance];
}

@end

想看Demo的同學請移駕-->TTS