Simple Video Recoder

StopNGo

• Documentation

========================================================================
DESCRIPTION:

StopNGo is a simple stop-motion animation QuickTime movie recorder that uses AVFoundation.

It creates a AVCaptureSession, AVCaptureDevice, AVCaptureVideoPreviewLayer, and AVCaptureStillImageOutput to preview and capture still images from a video capture device, then re-times each sample buffer to a frame rate of 5 fps and writes frames to disk using AVAssetWriter.

A frame rate of 5 fps means that 5 still images will result in a 1 second long movie. This value is hard coded in the sample but may be changed as required by the developer.

========================================================================
BUILD REQUIREMENTS:

Xcode 4.2 or later; iPhone iOS SDK 5.0 or later.

========================================================================
RUNTIME REQUIREMENTS:

iOS 5.0 or later. This app will not produce camera output on the iOS simulator.



========================================================================
Copyright (C) 2011 Apple Inc. All rights reserved.

• Design     
  
  
  
  
  
  
  
     

       

•  Code    

StopNGoAppDelegate.h

#import <UIKit/UIKit.h>

@interface StopNGoAppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@end

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StopNGoAppDelegate.m

#import "StopNGoAppDelegate.h"

@implementation StopNGoAppDelegate

@synthesize window = _window;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

    // Override point for customization after application launch.

    [self.window makeKeyAndVisible];

    return YES;

}

@end

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StopNGoViewController.h

 

#import <UIKit/UIKit.h>

#import <AVFoundation/AVFoundation.h>

@interface StopNGoViewController : UIViewController

{

BOOL started;

CMTime frameDuration;

CMTime nextPTS;

AVAssetWriter *assetWriter;

AVAssetWriterInput *assetWriterInput;

AVCaptureStillImageOutput *stillImageOutput;

NSURL *outputURL;

}

@property (nonatomic, retain) IBOutlet UIView *previewView;

@property (nonatomic, retain) IBOutlet UISlider *fpsSlider;

@property (nonatomic, retain) IBOutlet UIBarButtonItem *startFinishButton;

@property (nonatomic, retain) IBOutlet UIBarButtonItem *takePictureButton;

- (IBAction)takePicture:(id)sender;

- (IBAction)startStop:(id)sender;

@end

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StopNGoViewController.m

 

#import "StopNGoViewController.h"

#include <mach/mach_time.h>

#import <AssetsLibrary/AssetsLibrary.h>

@implementation StopNGoViewController

@synthesize previewView, fpsSlider, startFinishButton, takePictureButton;

- (BOOL)setupAVCapture

{

NSError *error = nil;

    // 5 fps - taking 5 pictures will equal 1 second of video

frameDuration = CMTimeMakeWithSeconds(1./5., 90000); 

AVCaptureSession *session = [AVCaptureSession new];

[session setSessionPreset:AVCaptureSessionPresetHigh];

// Select a video device, make an input

AVCaptureDevice *backCamera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:backCamera error:&error];

if (error)

return NO;

if ([session canAddInput:input])

[session addInput:input];

// Make a still image output

stillImageOutput = [AVCaptureStillImageOutput new];

if ([session canAddOutput:stillImageOutput])

[session addOutput:stillImageOutput];

// Make a preview layer so we can see the visual output of an AVCaptureSession

AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];

[previewLayer setVideoGravity:AVLayerVideoGravityResizeAspect];

[previewLayer setFrame:[previewView bounds]];

    // add the preview layer to the hierarchy

    CALayer *rootLayer = [previewView layer];

[rootLayer setBackgroundColor:[[UIColor blackColor] CGColor]];

[rootLayer addSublayer:previewLayer];

    // start the capture session running, note this is an async operation

    // status is provided via notifications such as AVCaptureSessionDidStartRunningNotification/AVCaptureSessionDidStopRunningNotification

    [session startRunning];

return YES;

}

static CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;};

- (BOOL)setupAssetWriterForURL:(NSURL *)fileURL formatDescription:(CMFormatDescriptionRef)formatDescription

{

    // allocate the writer object with our output file URL

NSError *error = nil;

assetWriter = [[AVAssetWriter alloc] initWithURL:fileURL fileType:AVFileTypeQuickTimeMovie error:&error];

if (error)

return NO;

    // initialized a new input for video to receive sample buffers for writing

    // passing nil for outputSettings instructs the input to pass through appended samples, doing no processing before they are written

assetWriterInput = [[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeVideo outputSettings:nil];

[assetWriterInput setExpectsMediaDataInRealTime:YES];

if ([assetWriter canAddInput:assetWriterInput])

[assetWriter addInput:assetWriterInput];

    // specify the prefered transform for the output file

CGFloat rotationDegrees;

switch ([[UIDevice currentDevice] orientation]) { 

case UIDeviceOrientationPortraitUpsideDown:

rotationDegrees = -90.;

break;

case UIDeviceOrientationLandscapeLeft: // no rotation

rotationDegrees = 0.;

break;

case UIDeviceOrientationLandscapeRight:

rotationDegrees = 180.;

break;

case UIDeviceOrientationPortrait:

case UIDeviceOrientationUnknown:

case UIDeviceOrientationFaceUp:

case UIDeviceOrientationFaceDown:

default:

rotationDegrees = 90.;

break;

}

CGFloat rotationRadians = DegreesToRadians(rotationDegrees);

[assetWriterInput setTransform:CGAffineTransformMakeRotation(rotationRadians)];

    // initiates a sample-writing at time 0

nextPTS = kCMTimeZero;

[assetWriter startWriting];

[assetWriter startSessionAtSourceTime:nextPTS];

    return YES;

}

- (IBAction)takePicture:(id)sender

{

    // initiate a still image capture, return immediately

    // the completionHandler is called when a sample buffer has been captured

AVCaptureConnection *stillImageConnection = [stillImageOutput connectionWithMediaType:AVMediaTypeVideo];

[stillImageOutput captureStillImageAsynchronouslyFromConnection:stillImageConnection 

completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *__strong error) {

 

          // set up the AVAssetWriter using the format description from the first sample buffer captured

          if ( !assetWriter ) {

 outputURL = [NSURL fileURLWithPath:[NSString stringWithFormat:@"%@/%llu.mov", NSTemporaryDirectory(), mach_absolute_time()]];

 //NSLog(@"Writing movie to \"%@\"", outputURL);

 CMFormatDescriptionRef formatDescription = CMSampleBufferGetFormatDescription(imageDataSampleBuffer);

 if ( NO == [self setupAssetWriterForURL:outputURL formatDescription:formatDescription] )

 return;

 }

          

 // re-time the sample buffer - in this sample frameDuration is set to 5 fps

 CMSampleTimingInfo timingInfo = kCMTimingInfoInvalid;

 timingInfo.duration = frameDuration;

 timingInfo.presentationTimeStamp = nextPTS;

 CMSampleBufferRef sbufWithNewTiming = NULL;

 OSStatus err = CMSampleBufferCreateCopyWithNewTiming(kCFAllocatorDefault, 

  imageDataSampleBuffer, 

  1, // numSampleTimingEntries

  &timingInfo, 

  &sbufWithNewTiming);

 if (err)

 return;

 

           // append the sample buffer if we can and increment presnetation time

 if ( [assetWriterInput isReadyForMoreMediaData] ) {

 if ([assetWriterInput appendSampleBuffer:sbufWithNewTiming]) {

 nextPTS = CMTimeAdd(frameDuration, nextPTS);

 }

 else {

 NSError *error = [assetWriter error];

 NSLog(@"failed to append sbuf: %@", error);

 }

 }

          

          // release the copy of the sample buffer we made

 CFRelease(sbufWithNewTiming);

}];

}

- (void)saveMovieToCameraRoll

{

    // save the movie to the camera roll

ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

//NSLog(@"writing \"%@\" to photos album", outputURL);

[library writeVideoAtPathToSavedPhotosAlbum:outputURL

completionBlock:^(NSURL *assetURL, NSError *error) {

if (error) {

NSLog(@"assets library failed (%@)", error);

}

else {

[[NSFileManager defaultManager] removeItemAtURL:outputURL error:&error];

if (error)

NSLog(@"Couldn't remove temporary movie file \"%@\"", outputURL);

}

outputURL = nil;

}];

}

- (IBAction)startStop:(id)sender

{

if (started) {

if (assetWriter) {

[assetWriterInput markAsFinished];

[assetWriter finishWriting];

assetWriterInput = nil;

assetWriter = nil;

[self saveMovieToCameraRoll];

}

[sender setTitle:@"Start"];

[takePictureButton setEnabled:NO];

}

else {

[sender setTitle:@"Finish"];

[takePictureButton setEnabled:YES];

}

started = !started;

}

- (void)didReceiveMemoryWarning

{

    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.

}

#pragma mark - View lifecycle

- (void)viewDidLoad

{

    [super viewDidLoad];

[self setupAVCapture];

// Do any additional setup after loading the view, typically from a nib.

}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation

{

    // Return YES for supported orientations

return ( UIInterfaceOrientationPortrait == interfaceOrientation );

}

@end

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 Copyright (C) 2011 Apple Inc. All Rights Reserved.

Click here for source code