How to detect a blow in the microphone with Unity

Question

I'm aware that there are several threads with the same problem, but i haven't been able to make their solution work. I ended up creating this class:

MicroController.h

#import Foundation/Foundation.h>

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

#import <UIKit/UIKit.h>

@interface MicroController : UIView < UITextFieldDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate, AVAudioSessionDelegate > {
    AVAudioRecorder *recorder;
    NSTimer *levelTimer;
    double lowPassResults;
}

- (void)levelTimerCallback:(NSTimer *)timer;
@end

MicroController.mm

#import "MicroController.h"


@implementation MicroController

- (id)init
{
    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;

        if ([recorder prepareToRecord] == YES){
            [recorder record];
        }else {
            int errorCode = CFSwapInt32HostToBig ([error code]); 
            NSLog(@"Error: %@ [%4.4s])" , [error localizedDescription], (char*)&errorCode); 

        }

        levelTimer = [NSTimer scheduledTimerWithTimeInterval: 0.03 target: self selector: @selector(levelTimerCallback:) userInfo: nil repeats: YES];
    } else
        NSLog([error description]); 

    // input 'level' is in meter.mAveragePower

    return self;
}

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

    const double ALPHA = 1.0; // 0.05f
    double peakPowerForChannel = pow(10, (0.05 * [recorder peakPowerForChannel:0]));
    lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;  

    if (lowPassResults > 0.55)
        NSLog(@"Mic blow detected");


    [recorder updateMeters];
    NSLog(@"Average input: %f Peak input: %f", [recorder averagePowerForChannel:0], [recorder peakPowerForChannel:0]);

}
    - (void)viewDidLoad {
        [super viewDidLoad];

        NSLog(@"initiated");

        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: 0.03 target: self selector: @selector(levelTimerCallback:) userInfo: nil repeats: YES];
        } else
            NSLog([error description]);

    }


    - (void)dealloc {
        [levelTimer release];
        [recorder release];
        [super dealloc];
    }
    @end

But I can't get to make the microphone work. I'm getting only this output, and the microphone never responds:

Average input: -120.000000 Peak input: -120.000000

Any idea about what can be wrong ?

Thanks for your help !

Answer 1

Well, I didn't think important to mention that i was working with unity, and it was the culprit.

Unity modifies some settings, so it's important to do this when you load your viewcontroller:

[[AVAudioSession sharedInstance]
 setCategory: AVAudioSessionCategoryPlayAndRecord
 error: &setCategoryError];
if (setCategoryError) {
    NSLog([setCategoryError description]);
}

Otherwise a perfectly written audiorecorder won't work correctly. And that was it..problem solved !

This bug was a PAIN to detect, I hope this message helps anyone else in the same predicament.

Answer 2

I have the same problem, in the case I use a Titanium appcelerator. In the simulator the class work correctly, but in the device not, Average input = -120 Here is the code:

//
//  MicController.h
//  Mic
//
//  Created by DekWilde on 10/26/11.
//  Copyright 2011 DekWilde. All rights reserved.
//

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

@interface MicController : NSObject {
    AVAudioRecorder *recorder;
    //NSTimer *levelTimer;
    double lowPassResults;  
}

+ (MicController *)sharedListener;
- (void)listen;
- (void)stop;
//- (void)levelTimerCallback:(NSTimer *)timer;
- (Float32)averagePower;
- (Float32)peakPower;
@end

and the MicController.m

    #import "MicController.h"


    static MicController *sharedListener = nil;


    @implementation MicController


    + (MicController *)sharedListener {
        @synchronized(self) {
            if (sharedListener == nil)
                [[self alloc] init];
        }

        return sharedListener;
    }

    - (void)dealloc {
        //[sharedListener stop];
        //[levelTimer release];
        [recorder release];
        [super dealloc];
    }

    #pragma mark -
    #pragma mark Listening

    - (void)listen {

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

        //kAudioFormatAppleIMA4
        //kAudioFormatMPEG4AAC
        /*
        NSMutableDictionary *settings = [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                         [NSNumber numberWithFloat: 44100.0],                 AVSampleRateKey,
                                         [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey,
                                         [NSNumber numberWithInt: 1],                         AVNumberOfChannelsKey,
                                         [NSNumber numberWithInt: AVAudioQualityMax],         AVEncoderAudioQualityKey,
                                         nil];
        */

        NSDictionary *settings = [[NSDictionary alloc] initWithObjectsAndKeys:
                                  [NSNumber numberWithFloat: 44100.0],                 AVSampleRateKey,
                                  [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey,
                                  [NSNumber numberWithInt: 2],                         AVNumberOfChannelsKey,
                                  [NSNumber numberWithInt: AVAudioQualityMax],         AVEncoderAudioQualityKey,
                                  nil];
                                  /*
                                  [NSNumber numberWithFloat: 44100.0],                  AVSampleRateKey,
                                  [NSNumber numberWithInt: kAudioFormatMPEG4AAC],      AVFormatIDKey,
                                  [NSNumber numberWithInt: 2],                          AVNumberOfChannelsKey,
                                  [NSNumber numberWithInt: AVAudioQualityMax],          AVEncoderAudioQualityKey,
                                  [NSNumber numberWithInt:16],                          AVLinearPCMBitDepthKey,
                                  [NSNumber numberWithBool:NO],                         AVLinearPCMIsBigEndianKey,
                                  [NSNumber numberWithBool:NO],                         AVLinearPCMIsFloatKey,
                                  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];
        } else
            NSLog([error description]); 
    }
    - (void)stop {
        [recorder release];
    }

    /*
    - (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;  

        //if (lowPassResults < 0.95)
        //NSLog(@"Mic blow detected");
        NSLog(@"Average input: %f Peak input: %f Low pass results: %f", [recorder averagePowerForChannel:0], [recorder peakPowerForChannel:0], lowPassResults);


    }
     */

    #pragma mark -
    #pragma mark Levels getters

    - (Float32)averagePower {
        [recorder updateMeters];

        const double ALPHA = 0.7;
        double peakPowerForChannel = pow(10, (0.05 * [recorder averagePowerForChannel:0]));
        lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;
        return [recorder averagePowerForChannel:0];
        //return lowPassResults;
        //NSLog(@"Average input: %f Peak input: %f Low pass results: %f", [recorder averagePowerForChannel:0], [recorder peakPowerForChannel:0], lowPassResults);

    }
    - (Float32)peakPower {
        [recorder updateMeters];

        const double ALPHA = 0.7;
        double peakPowerForChannel = pow(10, (0.05 * [recorder peakPowerForChannel:0]));
        lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;
        return [recorder peakPowerForChannel:0];
        //return lowPassResults;
        //NSLog(@"Average input: %f Peak input: %f Low pass results: %f", [recorder averagePowerForChannel:0], [recorder peakPowerForChannel:0], lowPassResults);

    }

    #pragma mark -
    #pragma mark Singleton Pattern

    + (id)allocWithZone:(NSZone *)zone {
        @synchronized(self) {
            if (sharedListener == nil) {
                sharedListener = [super allocWithZone:zone];
                return sharedListener;
            }
        }

        return nil;
    }

    - (id)copyWithZone:(NSZone *)zone {
        return self;
    }

    - (id)init {
        if ([super init] == nil)
            return nil;

        return self;
    }

    - (id)retain {
        return self;
    }

    - (unsigned)retainCount {
        return UINT_MAX;
    }

    //- (void)release {
        // Do nothing.
    //}

    - (id)autorelease {
        return self;
    }


@end

My question is: where i need to put this code that you has posted about the solution of this problem. . . How I can solve this problem?

Answer 3

OK, here is the solve: file "MicController.m"

#import "MicController.h"


static MicController *sharedListener = nil;


@implementation MicController


+ (MicController *)sharedListener {
    @synchronized(self) {
        if (sharedListener == nil)
            [[self alloc] init];
    }

    return sharedListener;
}

- (void)dealloc {
    //[sharedListener stop];
    //[levelTimer release];
    [recorder release];
    [super dealloc];
}

#pragma mark -
#pragma mark Listening

- (void)listen {

    [[AVAudioSession sharedInstance]
     setCategory: AVAudioSessionCategoryPlayAndRecord
     error: nil];




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

    //kAudioFormatAppleIMA4
    //kAudioFormatMPEG4AAC
    /*
    NSMutableDictionary *settings = [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                     [NSNumber numberWithFloat: 44100.0],                 AVSampleRateKey,
                                     [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey,
                                     [NSNumber numberWithInt: 1],                         AVNumberOfChannelsKey,
                                     [NSNumber numberWithInt: AVAudioQualityMax],         AVEncoderAudioQualityKey,
                                     nil];
    */

    NSDictionary *settings = [[NSDictionary alloc] initWithObjectsAndKeys:
                              [NSNumber numberWithFloat: 44100.0],                 AVSampleRateKey,
                              [NSNumber numberWithInt: kAudioFormatAppleLossless], AVFormatIDKey,
                              [NSNumber numberWithInt: 2],                         AVNumberOfChannelsKey,
                              [NSNumber numberWithInt: AVAudioQualityMax],         AVEncoderAudioQualityKey,
                              nil];
                              /*
                              [NSNumber numberWithFloat: 44100.0],                  AVSampleRateKey,
                              [NSNumber numberWithInt: kAudioFormatMPEG4AAC],      AVFormatIDKey,
                              [NSNumber numberWithInt: 2],                          AVNumberOfChannelsKey,
                              [NSNumber numberWithInt: AVAudioQualityMax],          AVEncoderAudioQualityKey,
                              [NSNumber numberWithInt:16],                          AVLinearPCMBitDepthKey,
                              [NSNumber numberWithBool:NO],                         AVLinearPCMIsBigEndianKey,
                              [NSNumber numberWithBool:NO],                         AVLinearPCMIsFloatKey,
                              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];
    } else
        NSLog([error description]); 
}
- (void)stop {
    [recorder release];
}

/*
- (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;  

    //if (lowPassResults < 0.95)
    //NSLog(@"Mic blow detected");
    NSLog(@"Average input: %f Peak input: %f Low pass results: %f", [recorder averagePowerForChannel:0], [recorder peakPowerForChannel:0], lowPassResults);


}
 */

#pragma mark -
#pragma mark Levels getters

- (Float32)averagePower {
    [recorder updateMeters];

    const double ALPHA = 0.7;
    double peakPowerForChannel = pow(10, (0.05 * [recorder averagePowerForChannel:0]));
    lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;
    return [recorder averagePowerForChannel:0];
    //return lowPassResults;
    //NSLog(@"Average input: %f Peak input: %f Low pass results: %f", [recorder averagePowerForChannel:0], [recorder peakPowerForChannel:0], lowPassResults);

}
- (Float32)peakPower {
    [recorder updateMeters];

    const double ALPHA = 0.7;
    double peakPowerForChannel = pow(10, (0.05 * [recorder peakPowerForChannel:0]));
    lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;
    return [recorder peakPowerForChannel:0];
    //return lowPassResults;
    //NSLog(@"Average input: %f Peak input: %f Low pass results: %f", [recorder averagePowerForChannel:0], [recorder peakPowerForChannel:0], lowPassResults);

}

#pragma mark -
#pragma mark Singleton Pattern

+ (id)allocWithZone:(NSZone *)zone {
    @synchronized(self) {
        if (sharedListener == nil) {
            sharedListener = [super allocWithZone:zone];
            return sharedListener;
        }
    }

    return nil;
}

- (id)copyWithZone:(NSZone *)zone {
    return self;
}

- (id)init {
    if ([super init] == nil)
        return nil;

    return self;
}

- (id)retain {
    return self;
}

- (unsigned)retainCount {
    return UINT_MAX;
}

- (void)release {
    // Do nothing.
}

- (id)autorelease {
    return self;
}


@end

Just add the code

 [[AVAudioSession sharedInstance]
     setCategory: AVAudioSessionCategoryPlayAndRecord
     error: nil];

above de void "- (void)listen {"

Thanks. Bye

Answer 4

Now that Unity 3.5 has added support for Microphone input I suggest that you do it in Unity so that you don't have to maintain the Cocoa code and make it easy to port this to Android/Web/Native in the future.

There are already some useful posts about this:

http://forum.unity3d.com/threads/123036-iOS-Microphone-input

http://forum.unity3d.com/threads/118215-Blow-detection-(Using-iOS-Microphone)