如何在ios 7中获得麦克风音量？

Question

有一个视图可以在ios 7中获得麦克风音量吗？

NSURL *url = [NSURL fileURLWithPath:@"/dev/null"];

NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys:
                          [NSNumber numberWithFloat: 44100.0],                 AVSampleRateKey,
                          [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey,
                          [NSNumber numberWithInt: 0],                         AVNumberOfChannelsKey,
                          [NSNumber numberWithInt: AVAudioQualityMax],         AVEncoderAudioQualityKey,
                          nil];

NSError *error;

recorder = [[AVAudioRecorder alloc] initWithURL:url settings:settings error:&error];

if (recorder) {
    //recorder.delegate = self;
    [recorder prepareToRecord];
    recorder.meteringEnabled = TRUE;
    [recorder record];
    levelTimer = [NSTimer scheduledTimerWithTimeInterval: 0.1 target: self selector: @selector(levelTimerCallback:) userInfo: nil repeats: YES];
} else {
    NSLog(@"");// mic error message
}

- (void)levelTimerCallback:(NSTimer *)timer {
    [recorder updateMeters];

    const double ALPHA = 0.05;
    double peakPowerForChannel = pow(10, (ALPHA * [recorder averagePowerForChannel:0]));
    db = 20* log10(peakPowerForChannel);
    db += taraturaDb;
    db = db < 0 ? 0 : db;
    lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;

    if (lowPassResults < 0.95) {
        NSLog(@"%f",db);
}

这在iOS6中起作用在iOS 7中不起作用

感谢

Answer 1

在初始化AVAudioRecorder之前放置这些行：

AVAudioSession *audioSession = [AVAudioSession sharedInstance];
[audioSession setActive:YES error:nil];
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryRecord error:nil];