捕捉视频帧

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
#import <AssetsLibrary/AssetsLibrary.h>

@interface ViewController : UIViewController<AVCaptureFileOutputRecordingDelegate>

@property (strong, nonatomic) AVCaptureSession *captureSession;
@property (strong, nonatomic) AVCaptureDeviceInput *videoInput;
@property (strong, nonatomic) AVCaptureDeviceInput *audioInput;
@property (strong, nonatomic) AVCaptureStillImageOutput *stillImageOutput;
@property (strong, nonatomic) AVCaptureMovieFileOutput *movieOutput;

@property (weak, nonatomic) IBOutlet UIButton *captureButton;
@property (weak, nonatomic) IBOutlet UISegmentedControl *modeControl;
@property (weak, nonatomic) IBOutlet UIImageView *thumbnailImageView;

- (IBAction)capture:(id)sender;
- (IBAction)updateMode:(id)sender;

@end

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController
@synthesize captureButton;
@synthesize modeControl;
@synthesize thumbnailImageView;

- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.captureSession = [[AVCaptureSession alloc] init];
//Optional: self.captureSession.sessionPreset = AVCaptureSessionPresetMedium;

AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];

self.videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:nil];
self.audioInput = [[AVCaptureDeviceInput alloc] initWithDevice:audioDevice error:nil];

self.stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
NSDictionary *stillImageOutputSettings = [[NSDictionary alloc] initWithObjectsAndKeys:
AVVideoCodecJPEG, AVVideoCodecKey, nil];
[self.stillImageOutput setOutputSettings:stillImageOutputSettings];

self.movieOutput = [[AVCaptureMovieFileOutput alloc] init];

// Setup capture session for taking pictures
[self.captureSession addInput:self.videoInput];
[self.captureSession addOutput:self.stillImageOutput];

AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.captureSession];
UIView *aView = self.view;
previewLayer.frame = CGRectMake(0, 70, self.view.frame.size.width, self.view.frame.size.height-140);
[aView.layer addSublayer:previewLayer];
}

- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

- (void) captureStillImage
{
AVCaptureConnection *stillImageConnection = [self.stillImageOutput.connections objectAtIndex:0];
if ([stillImageConnection isVideoOrientationSupported])
[stillImageConnection setVideoOrientation:AVCaptureVideoOrientationPortrait];

[[self stillImageOutput] captureStillImageAsynchronouslyFromConnection:stillImageConnection
completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error)
{
if (imageDataSampleBuffer != NULL)
{
NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
UIImage *image = [[UIImage alloc] initWithData:imageData];
[library writeImageToSavedPhotosAlbum:[image CGImage]
orientation:(ALAssetOrientation)[image imageOrientation]
completionBlock:^(NSURL *assetURL, NSError *error)
{
UIAlertView *alert;
if (!error)
{
alert = [[UIAlertView alloc] initWithTitle:@"Photo Saved"
message:@"The photo was successfully saved to you photos library"
delegate:nil
cancelButtonTitle:@"OK"
otherButtonTitles:nil, nil];
}
else
{
alert = [[UIAlertView alloc] initWithTitle:@"Error Saving Photo"
message:@"The photo was not saved to you photos library"
delegate:nil
cancelButtonTitle:@"OK"
otherButtonTitles:nil, nil];
}

[alert show];
}
];
}
else
NSLog(@"Error capturing still image: %@", error);
}];
}

- (NSURL *) tempFileURL
{
NSString *outputPath = [[NSString alloc] initWithFormat:@"%@%@", NSTemporaryDirectory(), @"output.mov"];
NSURL *outputURL = [[NSURL alloc] initFileURLWithPath:outputPath];
NSFileManager *manager = [[NSFileManager alloc] init];
if ([manager fileExistsAtPath:outputPath])
{
[manager removeItemAtPath:outputPath error:nil];
}
return outputURL;
}

- (IBAction)capture:(id)sender
{
if (self.modeControl.selectedSegmentIndex == 0)
{
// Picture Mode
[self captureStillImage];
}
else
{
// Video Mode
if (self.movieOutput.isRecording == YES)
{
[self.captureButton setTitle:@"Capture" forState:UIControlStateNormal];
[self.movieOutput stopRecording];
}
else
{
[self.captureButton setTitle:@"Stop" forState:UIControlStateNormal];
[self.movieOutput startRecordingToOutputFileURL:[self tempFileURL] recordingDelegate:self];
}
}
}

- (IBAction)updateMode:(id)sender
{
[self.captureSession stopRunning];
if (self.modeControl.selectedSegmentIndex == 0)
{
if (self.movieOutput.isRecording == YES)
{
[self.movieOutput stopRecording];
}
// Still Image Mode
[self.captureSession removeInput:self.audioInput];
[self.captureSession removeOutput:self.movieOutput];
[self.captureSession addOutput:self.stillImageOutput];
}
else
{
// Video Mode
[self.captureSession removeOutput:self.stillImageOutput];
[self.captureSession addInput:self.audioInput];
[self.captureSession addOutput:self.movieOutput];

// Set orientation of capture connections to portrait
NSArray *array = [[self.captureSession.outputs objectAtIndex:0] connections];
for (AVCaptureConnection *connection in array)
{
connection.videoOrientation = AVCaptureVideoOrientationPortrait;
}
}
[self.captureButton setTitle:@"Capture" forState:UIControlStateNormal];

[self.captureSession startRunning];
}

- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self.captureSession startRunning];
}

- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[self.captureSession stopRunning];
}

- (void)captureOutput:(AVCaptureFileOutput *)captureOutput
didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL
fromConnections:(NSArray *)connections
error:(NSError *)error
{
BOOL recordedSuccessfully = YES;
if ([error code] != noErr)
{
// A problem occurred: Find out if the recording was successful.
id value = [[error userInfo] objectForKey:AVErrorRecordingSuccessfullyFinishedKey];
if (value)
recordedSuccessfully = [value boolValue];
// Logging the problem anyway:
NSLog(@"A problem occurred while recording: %@", error);
}
if (recordedSuccessfully)
{
[self createThumbnailForVideoURL:outputFileURL];
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

[library writeVideoAtPathToSavedPhotosAlbum:outputFileURL
completionBlock:^(NSURL *assetURL, NSError *error)
{
UIAlertView *alert;
if (!error)
{
alert = [[UIAlertView alloc] initWithTitle:@"Video Saved"
message:@"The movie was successfully saved to you photos library"
delegate:nil
cancelButtonTitle:@"OK"
otherButtonTitles:nil, nil];
}
else
{
alert = [[UIAlertView alloc] initWithTitle:@"Error Saving Video"
message:@"The movie was not saved to you photos library"
delegate:nil
cancelButtonTitle:@"OK"
otherButtonTitles:nil, nil];
}

[alert show];
}
];
}
}

-(void)createThumbnailForVideoURL:(NSURL *)videoURL
{
AVURLAsset *myAsset = [[AVURLAsset alloc] initWithURL:videoURL options:[NSDictionary dictionaryWithObject:@"YES" forKey:AVURLAssetPreferPreciseDurationAndTimingKey]];

AVAssetImageGenerator *imageGenerator = [AVAssetImageGenerator assetImageGeneratorWithAsset:myAsset];
imageGenerator.appliesPreferredTrackTransform = YES; //Makes sure images are correctly rotated.

Float64 durationSeconds = CMTimeGetSeconds([myAsset duration]);
CMTime half = CMTimeMakeWithSeconds(durationSeconds/2.0, 600);
NSArray *times = [NSArray arrayWithObjects: [NSValue valueWithCMTime:half], nil];

[imageGenerator generateCGImagesAsynchronouslyForTimes:times
completionHandler:^(CMTime requestedTime, CGImageRef image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error)
{
if (result == AVAssetImageGeneratorSucceeded)
{
self.thumbnailImageView.image = [UIImage imageWithCGImage:image];
}
else if (result == AVAssetImageGeneratorFailed)
{
NSLog(@"Failed with error: %@", [error localizedDescription]);
}
}];
}

@end