iOS开发技巧之：麦克风音量实时检测

一、引入系统库

#import <AVFoundation/AVFoundation.h>

二、全局变量声明

@interface ViewController ()
{
    AVAudioRecorder *recorder;
    NSTimer *levelTimer;
}
@property(nonatomic,strong)UILabel *labelVoice;
@property(nonatomic,strong)CALayer *layerVoice;
 
@end

三、功能部分

1、UI部分

• (UILabel *)labelVoice { if (!_labelVoice) { _labelVoice = [[UILabel alloc]initWithFrame:CGRectMake(50, 100, 120, 50)]; _labelVoice.backgroundColor = [UIColor orangeColor];

    self.layerVoice = [CALayer layer];
    self.layerVoice.backgroundColor = [[UIColor greenColor]CGColor];
    self.layerVoice.frame = _labelVoice.bounds;
    [_labelVoice.layer addSublayer:_layerVoice];
  

  } return _labelVoice; } 2、功能部分

• (void)viewDidLoad { [super viewDidLoad]; [self.view addSubview:self.labelVoice];

  [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionDefaultToSpeaker | AVAudioSessionCategoryOptionMixWithOthers | AVAudioSessionCategoryOptionAllowBluetooth error:nil];

  /* 不需要保存录音文件 */ NSURL *url = [NSURL fileURLWithPath:@"/dev/null"];

  NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithFloat: 44100.0], AVSampleRateKey, [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey, [NSNumber numberWithInt: 2], AVNumberOfChannelsKey, [NSNumber numberWithInt: AVAudioQualityMax], AVEncoderAudioQualityKey, nil];

  NSError *error; recorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:&error]; if (recorder) { [recorder prepareToRecord]; recorder.meteringEnabled = YES; [recorder record]; levelTimer = [NSTimer scheduledTimerWithTimeInterval: 0.3 target: self selector: @selector(levelTimerCallback:) userInfo: nil repeats: YES]; } else { NSLog(@"%@", [error description]); } }

/* 该方法确实会随环境音量变化而变化，但具体分贝值是否准确暂时没有研究 */
- (void)levelTimerCallback:(NSTimer *)timer {
   [recorder updateMeters];
   
   float   level;                // The linear 0.0 .. 1.0 value we need.
   float   minDecibels = -60.0f; // use -80db Or use -60dB, which I measured in a silent room.
   float   decibels    = [recorder averagePowerForChannel:0];
   
   if (decibels < minDecibels)
   {
       level = 0.0f;
   }
   else if (decibels >= 0.0f)
   {
       level = 1.0f;
   }
   else
   {
       float   root            = 5.0f; //modified level from 2.0 to 5.0 is neast to real test
       float   minAmp          = powf(10.0f, 0.05f * minDecibels);
       float   inverseAmpRange = 1.0f / (1.0f - minAmp);
       float   amp             = powf(10.0f, 0.05f * decibels);
       float   adjAmp          = (amp - minAmp) * inverseAmpRange;
       
       level = powf(adjAmp, 1.0f / root);
   }
   
   /* level 范围[0 ~ 1], 转为[0 ~120] 之间 */
   dispatch_async(dispatch_get_main_queue(), ^{
       NSLog(@"voice updated :%f",level * 120);
       self.layerVoice.frame = CGRectMake(0, 0, level * 120, 50);
   });
}

文章转载于：blog.csdn.net/vkooy/artic…