Question

我试图像这样获得麦克风音量：在头文件中：

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
#import <CoreAudio/CoreAudioTypes.h>

@interface AlarmViewController : UIViewController {
    AVAudioRecorder *recorder;
    NSTimer *levelTimer;
}

@property (strong, nonatomic) IBOutlet UISegmentedControl *segmentedControl;
@property (strong, nonatomic) IBOutlet UILabel *timeLabel;

- (void)timeChange:(NSTimer *)timer;
- (void)levelTimerCallback:(NSTimer *)timer;

@end

在实施文件中：

- (void)viewDidLoad
{
    [super viewDidLoad];

    NSURL *url = [NSURL fileURLWithPath:@"/dev/null"];
    NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithFloat:44100.0], AVSampleRateKey, [NSNumber numberWithInt:kAudioFormatAppleLossless], AVFormatIDKey, [NSNumber numberWithInt:1], 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:0.5 target:self selector:@selector(levelTimerCallback:) userInfo:nil repeats:YES];
    }
    else {
        NSLog(@"%@", [error description]);
    }
}

- (void)levelTimerCallback:(NSTimer *)timer {
    [recorder updateMeters];
    NSLog(@"Average input: %f Peak input: %f", [recorder averagePowerForChannel:0], [recorder peakPowerForChannel:0]);
}

因此，在日志中它返回以下内容：

2014-06-29 16:31:42.400 NightLight[1140:388914] Average input: -120.000000 Peak input: -120.000000

我不知道该怎么办？我确信它可以在iPhone的隐私设置中使用麦克风。

Answer 1

事实证明，您需要使用AVAudioSession为应用程序设置上下文。在 [super viewDidLoad];

之后的 - （void）viewDidLoad 中添加以下代码

// Set audio context to app
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
[audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];
[audioSession setActive:YES error:nil];

无法获得麦克风声级

1 个答案: