AVFoundation question(Asked in general discussion)

#import <Foundation/Foundation.h>
#import <CoreVideo/CoreVideo.h>
#import <AVFoundation/AVFoundation.h>

@interface CameraSessionManager : NSObject {
    AVCaptureSession *captureSession;
    AVCaptureVideoPreviewLayer *previewLayer;
    AVCaptureVideoDataOutput *captureOutput;
}
- (id)init;
- (void)addVideoInput;
- (void)addPreviewLayer;
@property (nonatomic,retain) AVCaptureSession *captureSession;
@property (nonatomic,retain) AVCaptureVideoPreviewLayer *previewLayer;
@property (nonatomic,retain) AVCaptureVideoDataOutput *captureOutput;
@end

#import \"CameraSessionManager.h\"


@implementation CameraSessionManager
@synthesize captureSession, captureOutput,previewLayer;
- (id)init{
    self = [super init];
    if(self){
        [self addVideoInput];
        [self addPreviewLayer];
    }
    return self;
}

//GOAL:Sets up the videos input
- (void)addVideoInput{
    self.captureSession = [[AVCaptureSession alloc]init];//initialize capture session
    [self.captureSession setSessionPreset:AVCaptureSessionPresetMedium];
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];//set up a capture device with Media Type Video
    if(device){
        NSError *error;
        AVCaptureDeviceInput *videoIn = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
        
        if(!error){
            if([self.captureSession canAddInput:videoIn])
                [self.captureSession addInput:videoIn];
            else
                NSLog(@\"Cannot add video input\");
        }
        else
            NSLog(@\"Couldent create video input\");
    }
    else
        NSLog(@\"Couldent create video capture device\");
    [self.captureSession release];
    
}
//GOAL:Sets up the preview layer
- (void)addPreviewLayer{
    self.previewLayer = [[AVCaptureVideoPreviewLayer alloc]initWithSession:self.captureSession];//initialize the preview with the capture session
    [self.previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];//set the previews layer view size
    [self.previewLayer release];
}
- (void)dealloc{
    [self.captureSession stopRunning];
    [self.captureSession release];
    [self.previewLayer release];
    [self.captureOutput release];
    [super dealloc];
}

#import <Foundation/Foundation.h>
#import \"CameraSessionManager.h\"

@interface CameraCaptureManager : CameraSessionManager<AVCaptureVideoDataOutputSampleBufferDelegate> {

@private
    UIImage *frame; 
    AVCaptureStillImageOutput *captureStillImage;
}
- (id)init;
- (void)addVideoOutput;
- (void)addStillImageOutput;
- (UIImage*)captureImage;
- (UIImage*)imageFromSampleBuffer:(CMSampleBufferRef)sampleBuffer;
@property (nonatomic,retain) UIImage *frame;
@property (nonatomic,retain) AVCaptureStillImageOutput *captureStillImage;
@end

#import \"CameraCaptureManager.h\"


@implementation CameraCaptureManager
@synthesize frame;
@synthesize captureStillImage;

- (id)init{
    self = [super init];
    if(self){
        frame = [[UIImage alloc]init];
        [self addVideoOutput];
        [self addStillImageOutput];
    }
    return self;
}

//GOAL:Sets up the videos output
- (void)addVideoOutput{
    
    self.captureOutput = [[AVCaptureVideoDataOutput alloc]init];//initialize video output
    self.captureOutput.videoSettings = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:@\"kCVPixelBufferPixelFormatTypeKey\"];
    self.captureOutput.minFrameDuration = CMTimeMake(1, 15);

    if([self.captureSession canAddOutput:self.captureOutput])//check if the capture session can add the output
        [self.captureSession addOutput:self.captureOutput];//add the output to the capture session
    else 
        NSLog(@\"Capture Session can't add output\");
    
    dispatch_queue_t queue = dispatch_queue_create(\"Sample Delegate Queue\", NULL);
    [self.captureOutput setSampleBufferDelegate:self queue:queue];
    dispatch_release(queue);
    
    [self.captureOutput release];
}
- (void)addStillImageOutput{
    self.captureStillImage = [[AVCaptureStillImageOutput alloc]init];
    [self.captureStillImage setOutputSettings:[NSDictionary dictionaryWithObjectsAndKeys:AVVideoCodecJPEG,AVVideoCodecKey, nil]];
    if([self.captureSession canAddOutput:self.captureStillImage])
        [self.captureSession addOutput:self.captureStillImage];
    else
        NSLog(@\"Capture Session could not add still image output\");
    [self.captureStillImage release];
}
- (UIImage*)captureImage{
    AVCaptureConnection *videoConnection = nil;
    
    for(AVCaptureConnection *connection in captureStillImage.connections){
        for(AVCaptureInputPort *port in connection.inputPorts){
            if([port.mediaType isEqual:AVMediaTypeVideo]){
                videoConnection = connection;
                break;
            }            
        }
        if(videoConnection){
            break;
        }
    }
    
    [self.captureStillImage captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
        frame = [self imageFromSampleBuffer:imageDataSampleBuffer];
    }];
     
    return frame;
}

- (UIImage*)imageFromSampleBuffer:(CMSampleBufferRef)sampleBuffer{
    
    NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:sampleBuffer];
    UIImage *image = [UIImage imageWithData:imageData];
    return image;
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    
}
- (void)dealloc{
    [frame release];frame = nil;
    [super dealloc];
}

#import <UIKit/UIKit.h>
#import \"CameraCaptureManager.h\"
@interface CameraEdgeDetectionViewController : UIViewController {
    UIImageView *captureImageView;
    CameraCaptureManager *sessionManager;
}
- (id)init;
- (void)setUpCameraSession;
- (void)takePicture;
@property (nonatomic,retain) UIImageView *captureImageView;
@property (nonatomic,retain) CameraCaptureManager *sessionManager;
@end

#import \"CameraEdgeDetectionViewController.h\"

@implementation CameraEdgeDetectionViewController
@synthesize sessionManager;
@synthesize captureImageView;

#pragma mark - Initializers
- (id)init{
    self = [super init];
    if(self){
        [self setUpCameraSession];
    }
    return  self;
}

#pragma mark - View lifecycle
- (void)viewDidLoad{
       [super viewDidLoad];
}
- (void)viewDidUnload{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}
- (void)viewDidAppear:(BOOL)animated{
    captureImageView = [[UIImageView alloc]init];
    [captureImageView setFrame:CGRectMake(30, 30, 50, 50)];
    [self.view addSubview:captureImageView];
    
    UIButton *captureButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [captureButton setFrame:CGRectMake(30, 90, 50, 50)];
    [captureButton addTarget:self action:@selector(takePicture) forControlEvents:UIControlEventTouchDown];
    [self.view addSubview:captureButton];

    [super viewDidAppear:animated];
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation{
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

#pragma mark - Camera Session
//GOAL:Sets up the camera session and adds the preview layer to the screen
- (void)setUpCameraSession{
    
    //initialize the session manager
    sessionManager = [[CameraCaptureManager alloc]init];
    
    //create Previews layer rect and position
    CGRect layerRect = self.view.layer.bounds;
    CGPoint layerPosition = CGPointMake(CGRectGetMidX(layerRect), CGRectGetMidY(layerRect));    
    
    //set the previews layer and rect
    [self.sessionManager.previewLayer setFrame:layerRect];
    [self.sessionManager.previewLayer setPosition:layerPosition];
    
    //add preview layer to views layer
    [self.view.layer addSublayer:self.sessionManager.previewLayer];
    
    //start capture session
    [self.sessionManager.captureSession startRunning];
}

//GOAL:When the user taps the button on the screen this update the imageview to the image taken
- (void)takePicture{
    [self.captureImageView setImage:[self.sessionManager captureImage]];
}

#pragma mark - Memory
- (void)didReceiveMemoryWarning{
    [super didReceiveMemoryWarning];
}
- (void)dealloc{
    [self.captureImageView release];self.captureImageView = nil;
    [self.sessionManager release];self.sessionManager = nil;
    [super dealloc];
}