在IOS中，在做语音识别中，需要对语音进行抓取。

#import "GetAudioViewController.h"

#import <AVFoundation/AVFoundation.h>

#import <UIKit/UIKit.h>

#import <ImageIO/ImageIO.h>

#import <MobileCoreServices/MobileCoreServices.h>

#import <QuartzCore/QuartzCore.h>

@interface GetAudioViewController ()

{

    AVAudioPlayer *_player;

    AVAudioRecorder *_audiorecord;

    NSTimer* _timerForPitch;

    CAShapeLayer *_shapeLayer;

    CADisplayLink* _displayLink;

    __weak IBOutlet UIProgressView *_audioPower;

    __weak IBOutlet UIButton *_record;

    __weak IBOutlet UIButton *_pause;

    __weak IBOutlet UIButton *_resume;

    __weak IBOutlet UIButton *_stop;

    __weak IBOutlet UIView *_viewForWave;

    float Pitch;

    NSInteger _recordEncoding;

    CFTimeInterval _firstTimestamp;

    NSInteger _loopCount;

}

@end

@implementation GetAudioViewController

- (void)viewDidLoad {

    [super viewDidLoad];

}

-(void)cratePath:(NSString*)path

{

    NSFileManager* filemanager = [NSFileManager defaultManager];

    if(![filemanager fileExistsAtPath:path])

        [filemanager createDirectoryAtPath:path

               withIntermediateDirectories:YES

                                attributes:nil

                                     error:nil];

}

- (UIBezierPath *)pathAtInterval:(NSTimeInterval) interval

{

    UIBezierPath *path = [UIBezierPath bezierPath];

    [path moveToPoint:CGPointMake(0, _viewForWave.bounds.size.height / 2.0)];

    CGFloat fractionOfSecond = interval - floor(interval);

    CGFloat yOffset = _viewForWave.bounds.size.height * sin(fractionOfSecond * M_PI * Pitch*8);

    [path addCurveToPoint:CGPointMake(_viewForWave.bounds.size.width, _viewForWave.bounds.size.height / 2.0)

            controlPoint1:CGPointMake(_viewForWave.bounds.size.width / 2.0, _viewForWave.bounds.size.height / 2.0 - yOffset)

            controlPoint2:CGPointMake(_viewForWave.bounds.size.width / 2.0, _viewForWave.bounds.size.height / 2.0 + yOffset)];

    return path;

}

- (void)addShapeLayer

{

    _shapeLayer = [CAShapeLayer layer];

    _shapeLayer.path = [[self pathAtInterval:2.0] CGPath];

    _shapeLayer.fillColor = [[UIColor redColor] CGColor];

    _shapeLayer.lineWidth = 1.0;

    _shapeLayer.strokeColor = [[UIColor whiteColor] CGColor];

    [_viewForWave.layer addSublayer:_shapeLayer];

}

- (void)handleDisplayLink:(CADisplayLink *)displayLink

{

    if (!_firstTimestamp)

        _firstTimestamp = displayLink.timestamp;

    _loopCount++;

    NSTimeInterval elapsed = (displayLink.timestamp - _firstTimestamp);

    _shapeLayer.path = [[self pathAtInterval:elapsed] CGPath];

}

- (void)startDisplayLink

{

    _displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(handleDisplayLink:)];

    [_displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

}

- (IBAction)recordClick:(id)sender {

    _viewForWave.hidden = NO;

    [self addShapeLayer];

    [self startDisplayLink];

    NSLog(@"startRecording");

    _audiorecord = nil;

    AVAudioSession *audioSession = [AVAudioSession sharedInstance];

    [audioSession setCategory:AVAudioSessionCategoryRecord error:nil];

    NSMutableDictionary *recordSettings = [[NSMutableDictionary alloc] initWithCapacity:10];

    if(_recordEncoding == 6)

    {

        [recordSettings setObject:[NSNumber numberWithInt: kAudioFormatLinearPCM] forKey: AVFormatIDKey];

        [recordSettings setObject:[NSNumber numberWithFloat:44100.0] forKey: AVSampleRateKey];

        [recordSettings setObject:[NSNumber numberWithInt:2] forKey:AVNumberOfChannelsKey];

        [recordSettings setObject:[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey];

        [recordSettings setObject:[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsBigEndianKey];

        [recordSettings setObject:[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsFloatKey];

    }

    else

    {

        NSNumber *formatObject;

        switch (_recordEncoding) {

            case 1:

                formatObject = [NSNumber numberWithInt: kAudioFormatMPEG4AAC];

                break;

            case 2:

                formatObject = [NSNumber numberWithInt: kAudioFormatAppleLossless];

                break;

            case 3:

                formatObject = [NSNumber numberWithInt: kAudioFormatAppleIMA4];

                break;

            case 4:

                formatObject = [NSNumber numberWithInt: kAudioFormatiLBC];

                break;

            case 5:

                formatObject = [NSNumber numberWithInt: kAudioFormatULaw];

                break;

            default:

                formatObject = [NSNumber numberWithInt: kAudioFormatAppleIMA4];

        }

        [recordSettings setObject:formatObject forKey: AVFormatIDKey];

        [recordSettings setObject:[NSNumber numberWithFloat:44100.0] forKey: AVSampleRateKey];

        [recordSettings setObject:[NSNumber numberWithInt:2] forKey:AVNumberOfChannelsKey];

        [recordSettings setObject:[NSNumber numberWithInt:12800] forKey:AVEncoderBitRateKey];

        [recordSettings setObject:[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey];

        [recordSettings setObject:[NSNumber numberWithInt: AVAudioQualityHigh] forKey: AVEncoderAudioQualityKey];

    }

    NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSString *docsDir = [dirPaths objectAtIndex:0];

    NSString *soundFilePath = [docsDir

                               stringByAppendingPathComponent:@"recordTest.caf"];

    NSURL *url = [NSURL fileURLWithPath:soundFilePath];

    NSError *error = nil;

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

    _audiorecord.meteringEnabled = YES;

    if ([_audiorecord prepareToRecord] == YES){

        _audiorecord.meteringEnabled = YES;

        [_audiorecord record];

        _timerForPitch =[NSTimer scheduledTimerWithTimeInterval: 0.01 target: self selector: @selector(levelTimerCallback:) userInfo: nil repeats: YES];

    }else {

        //int errorCode = CFSwapInt32HostToBig ([error code]);

        //NSLog(@"Error: %@ [%4.4s])" , [error localizedDescription], (char*)&errorCode);

    }

}

- (void)levelTimerCallback:(NSTimer *)timer {

    [_audiorecord updateMeters];

//    float linear = pow (10, [_audiorecord peakPowerForChannel:0] / 20);

    float linear1 = pow (10, [_audiorecord averagePowerForChannel:0] / 20);

    if (linear1>0.03) {

        Pitch = linear1+.20;//pow (10, [audioRecorder averagePowerForChannel:0] / 20);//[audioRecorder peakPowerForChannel:0];

    }

    else {

        Pitch = 0.0;

    }

//    //Pitch =linear1;

//    NSLog(@"Pitch==%f",Pitch);

//    _customRangeBar.value = http://www.mamicode.com/Pitch;//linear1+.30;

    [_audioPower setProgress:Pitch];

//    float minutes = floor(_audiorecord.currentTime/60);

//    float seconds = _audiorecord.currentTime - (minutes * 60);

//    NSString *time = [NSString stringWithFormat:@"%0.0f.%0.0f",minutes, seconds];

//    [self.statusLabel setText:[NSString stringWithFormat:@"%@ sec", time]];

//    NSLog(@"recording");

}

- (IBAction)pauseClick:(id)sender {

    NSLog(@"stopRecording");

    // kSeconds = 0.0;

    _viewForWave.hidden = YES;

    [_audiorecord stop];

    [self stopDisplayLink];

    _shapeLayer.path = [[self pathAtInterval:0] CGPath];

    [_timerForPitch invalidate];

    _timerForPitch = nil;

}

- (void)stopDisplayLink

{

    [_displayLink invalidate];

    _displayLink = nil;

}

- (IBAction)resumeClick:(id)sender {

    AVAudioSession *audioSession = [AVAudioSession sharedInstance];

    [audioSession setCategory:AVAudioSessionCategoryPlayback error:nil];

    NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSString *docsDir = [dirPaths objectAtIndex:0];

    NSString *soundFilePath = [docsDir stringByAppendingPathComponent:@"recordTest.caf"];

    NSURL *url = [NSURL fileURLWithPath:soundFilePath];

    NSError *error;

    _player = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error];

    _player.numberOfLoops = 0;

    [_player play];

}

- (IBAction)stopClick:(id)sender {

    [_player stop];

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

}

@end

代码全部在这里了。其中

_viewForWave是一个波段的反应图。有兴趣的朋友可以自己去写一个，美化，参考我的写的话，记得给我留言。

IOS语音录取