How to display audio meter on an iPhone

Question

I have an audio recorder and I was wondering if anyone has a code to show a audio meter (the bar that most of audio recorders have which shows the level of input audio).

score 4 · Answer 1 · edited May 19 '11 at 11:21

4

Apple's SpeakHere example code includes a LevelView class which seems to be exactly what you are looking for.

edited May 19 '11 at 11:21

Bill the Lizard

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answered Apr 16 '11 at 14:59

Jonah

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This apple sample code is anything but simple to implement it within your own project. Extremely confusing and needlessly complicated – Sam B Jul 16 '13 at 21:55
Yeah. It is not simple at all. What it does pretty simple but code is so much confusing... – bpolat Sep 09 '14 at 17:45
@SamB Can I use apple's SpeakHear example in my project? – Gajendra K Chauhan May 25 '15 at 07:00
The link is broken.. Can anyone share the level view class? – Neil Galiaskarov Jul 10 '17 at 15:52
Looks like there's a copy of the SpeakHere example at https://github.com/robovm/apple-ios-samples/tree/master/SpeakHere – Jonah Jul 10 '17 at 18:30

score 2 · Answer 2 · answered May 08 '13 at 10:39

Heres an example that calculates output and prints it:

- (void)viewDidLoad {
    [super viewDidLoad];

    NSURL *url = [NSURL fileURLWithPath:@"/dev/null"]; // Your audio save path

    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: 0.03 target: self selector: @selector(levelTimerCallback:) userInfo: nil repeats: YES];
    } 
}


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

    const double ALPHA = 0.05;
    double peakPowerForChannel = pow(10, (0.05 * [recorder peakPowerForChannel:0]));
    lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;
    NSLog(@"%f",(lowPassResults*100.0f));
}

Depending on the lowPassResults you can animate a view accordingly.

'lowPassResults' is used uninitialized, is it iVar? What is initial value for it? — myeyesareblind, Aug 28 '13 at 19:25

How to display audio meter on an iPhone

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