(二)AVFoundation 音频播放和录制

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/**
 激活音频会话
 */
-(void)activeAudioSessionCagegory{
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    NSError *err = nil;
    
    // 注意:
    // 如果分类允许后台播放, 则应该打开Capabilities 中 background Modes, 继而勾选打开后台播放选项
    if(![audioSession setCategory:AVAudioSessionCategoryPlayback error:&err]){
        
        NSLog(@"category err: %@",err);
    }
    
    
    if(![audioSession setActive:YES error:&err]){
        NSLog(@"active err: %@ ",err);
    }
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    
    [self activeAudioSessionCagegory];
    
    return YES;
}

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-(void)initSetupPlayer{
    
    NSURL *fileUrl = [[NSBundle mainBundle] URLForResource:@"" withExtension:@""];
    NSError *err = nil;
    //   注意: player 必须使用强指针引用
    self.player = [[AVAudioPlayer alloc] initWithContentsOfURL:fileUrl error:&err];
    
    if (self.player != nil) {
        self.player.numberOfLoops = -1; // 循环播放
        // 说明: prepareToPlay 方法是可选的, 在调用 player 的 play 方法前 也会自动调用, 作用是取得需要的音频硬件并预加载
        // Audio Queue 的缓冲区, 降低调用 play 方法后的延时
        [self.player prepareToPlay]; // 缓冲
    }
    
}

-(void)play{
    [self.player play];
}


/**
 通过pause 和 stop 方法停止的音频会继续播放.
 最主要的区别在底层处理上, 调用 stop 方法会撤销调用 prepareToPlay时所作的设置, 而调用 pause 方法则不会.
 */
-(void)pause{
    [self.player pause];
}

-(void)stop{
    [self.player stop];
    self.player.currentTime = 0.0f;
}


/**
 音量 0~1
 */
-(void)voiceSlider:(UISlider *)slider{
    self.player.volume = slider.value;
}

/**
 声道 -1~1
 */
-(void)vocalTractSlider:(UISlider *)slider{
    self.player.pan = slider.value * 2.0 -1.0;
}

/**
 速率 0.5 ~ 2
 */
-(void)speedSlider:(UISlider *)slider{
    self.player.rate = slider.value * 1.5 + 0.5;
    // 注意:
    // 如果要改变速率, 在初始化AVAudioPlayer 时, 应该做出如下设置
    // self.player.enableRate = YES;
}

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- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 添加中断通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(udioSessionInterruptionNotice:) name:AVAudioSessionInterruptionNotification object:[AVAudioSession sharedInstance]];
    
}
-(void)udioSessionInterruptionNotice:(NSNotification *)notice{
    
    
    NSDictionary *infoDic = notice.userInfo;
    
    AVAudioSessionInterruptionType interruptType = [infoDic[AVAudioSessionInterruptionTypeKey] unsignedIntegerValue];
    
    // 判断中断的类型
    if(interruptType == AVAudioSessionInterruptionTypeBegan){
        // 中断开始, 设置停止音乐
        [self.player pause];
    }
    else{
        
        // 中断结束, 判断是否允许继续播放
        AVAudioSessionInterruptionOptions interruptOption = [infoDic[AVAudioSessionInterruptionOptionKey] unsignedIntegerValue];
        if (interruptOption == AVAudioSessionInterruptionOptionShouldResume) {
            // 允许继续播放, 则继续播放
            [self.player play];
        }
    
    }
    
}

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   // 音频线路改变通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(audioSessionRouteChangeNotice:) name:AVAudioSessionRouteChangeNotification object:[AVAudioSession sharedInstance]];


/**
 音频线路变化通知
 
 播放音频期间插入耳机, 音频输出线路变成耳机插孔并继续播放.
 断开耳机连接,音频线路再次回到设备的内置扬声器播放.
 虽然线路变化和预期一样,不过按照苹果官方文档,认为该音频应该处于静音状态.
 */
-(void)audioSessionRouteChangeNotice:(NSNotification *)notice{
    
    NSDictionary *infoDic = notice.userInfo;
    AVAudioSessionRouteChangeReason routerChangeReason = [infoDic[AVAudioSessionRouteChangeReasonKey] unsignedIntegerValue];
    
    if (routerChangeReason == AVAudioSessionRouteChangeReasonOldDeviceUnavailable) {
        
        AVAudioSessionRouteDescription *previousRoute = infoDic[AVAudioSessionRouteChangePreviousRouteKey];
        
        AVAudioSessionPortDescription *previousOutput = [previousRoute.outputs firstObject];
        
        if ([previousOutput.portType isEqualToString:AVAudioSessionPortHeadphones]) {
            
            // 停止播放音乐
            [self.player stop];
        }
    }
}

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- (void)viewDidLoad {
    [super viewDidLoad];
   
   
    NSURL *fileUrl =  [NSURL fileURLWithPath:[[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"record.caf"]];
    
    /**
     在录制过程中,Core Audio Format (caf) 通常是最好的容器格式,因为他和内容无关可以保存Core Audio 支持的任何音频格式.
     在设置字典中是定的键值信息也是值得讨论一番的
     */
    NSDictionary *settting = @{
                               AVFormatIDKey : @(kAudioFormatAppleIMA4),
                               AVSampleRateKey : @(22050.0f),
                               AVNumberOfChannelsKey : @(1)
                               };
    
    NSError *err = nil;
    self.recorder = [[AVAudioRecorder alloc] initWithURL:fileUrl settings:settting error:&err];
    
    if (self.recorder) {
        
        self.recorder.delegate = self;
        
        [self.recorder prepareToRecord];
    }
}



-(void)startRecord{
    
    [self.recorder record];
}


-(void)recordFinish{
    [self.recorder stop];
}



#pragma mark- AVAudioRecorderDelegate
/**
 音频录制完成调用
 */
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag{
    
    if(flag){
        
        // 一般把录制好的音频复制或者剪切到目录的文件夹下
        NSURL *sourceUrl = self.recorder.url;
        
        NSURL *targetUrl = [NSURL fileURLWithPath:@"目标文件夹/音频文件名.caf"];
        
        NSError *err = nil;
        [[NSFileManager defaultManager] copyItemAtURL:sourceUrl toURL:targetUrl error:&err];
        
    }
}

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self.recorder.meteringEnabled = YES;

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self.player.meteringEnabled = YES;

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-(void)startMeterTimer{
    [self.link invalidate];
    CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(updateMeter)];
    link.frameInterval = 4;   // 间隔时间为刷帧率的 1/4
    [link addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
    self.link = link;
}

-(void)stopMeterTimer{
    [self.link invalidate];
    self.link = nil;
}

/**
 返回用于表示声音分贝（dB）等级的浮点值，这个值的范围是 -160dB ~ 0dB
 */
-(void)updateMeter{
    
    [self.recorder updateMeters];
    CGFloat num1 = [self.recorder averagePowerForChannel:0];
    CGFloat num2 = [self.recorder peakPowerForChannel:0];
    NSLog(@"录音平均分贝: %f, 峰值分贝: %f",num1, num2);
    
    
    
//    [self.player updateMeters];  // 刷新
//
//    CGFloat num1 = [self.player averagePowerForChannel:0];
//    CGFloat num2 = [self.player peakPowerForChannel:0];
//
//    NSLog(@"播放平均分贝：%f, 峰值分贝：%f", num1, num2);
    
}

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[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord error: nil];
 [[AVAudioSession sharedInstance] setActive: YES error: nil]; 
 UInt32 doChangeDefault = 1; 
 AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryDefaultToSpeaker, sizeof(doChangeDefault), &doChangeDefault);

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  AVAudioSession *audioSession = [AVAudioSession sharedInstance];  
  NSError *err = nil; 
  [audioSession setCategory :AVAudioSessionCategoryPlayback error:&err];