我使用AVCaptureVideoDataOutput在显示预览中显示相机图像。我的目的是使用两个调度队列，一个用于显示会话队列，另一个用于图像处理。这样我就可以在预览中显示图像然后在后台显示图像，我可以进行图像处理。这就是我使用AVCaptureVideoDataOutput和AVCaptureVideoDataOutputSampleBufferDelegate。
AVCaptureVideoDataOutput已正确设置为链接到AVCaptureSession以便在预览时显示。但委托方法
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
来检索图像并继续进行图像处理。我的设置可能有什么问题？代码如下所示。
#import "AVCamViewController.h"
#import <AVFoundation/AVFoundation.h>
#import <AssetsLibrary/AssetsLibrary.h>
#import "AVCamPreviewView.h"
#import "ImageProcessing.h"
static void * CapturingStillImageContext = &CapturingStillImageContext;
static void * RecordingContext = &RecordingContext;
static void * SessionRunningAndDeviceAuthorizedContext = &SessionRunningAndDeviceAuthorizedContext;
@interface AVCamViewController() <AVCaptureVideoDataOutputSampleBufferDelegate>
// For use in the storyboards.
@property (weak, nonatomic) IBOutlet UIButton *cpuButton;
@property (weak, nonatomic) IBOutlet UIButton *gpuButton;
@property (weak, nonatomic) IBOutlet AVCamPreviewView *previewView;
@property (nonatomic, weak) IBOutlet UIButton *cameraButton;
- (IBAction)changeCamera:(id)sender;
- (IBAction)focusAndExposeTap:(UIGestureRecognizer *)gestureRecognizer;
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer;
// Session management.
@property (nonatomic) dispatch_queue_t sessionQueue; // Communicate with the session and other session objects on this queue.
@property (nonatomic) AVCaptureSession *session;
@property (nonatomic) AVCaptureDeviceInput *videoDeviceInput;
@property (nonatomic) AVCaptureVideoDataOutput *vid_Output;
// Utilities.
@property (nonatomic) UIBackgroundTaskIdentifier backgroundRecordingID;
@property (nonatomic, getter = isDeviceAuthorized) BOOL deviceAuthorized;
@property (nonatomic, readonly, getter = isSessionRunningAndDeviceAuthorized) BOOL sessionRunningAndDeviceAuthorized;
@property (nonatomic) BOOL lockInterfaceRotation;
@property (nonatomic) id runtimeErrorHandlingObserver;
//fps
//@property int fps;
//Image processing management
@property (nonatomic) dispatch_queue_t im_processingQueue;
@property bool cpu_processing;
@property bool gpu_processing;
@end
@implementation AVCamViewController
- (BOOL)isSessionRunningAndDeviceAuthorized
{
return [[self session] isRunning] && [self isDeviceAuthorized];
}
+ (NSSet *)keyPathsForValuesAffectingSessionRunningAndDeviceAuthorized
{
return [NSSet setWithObjects:@"session.running", @"deviceAuthorized", nil];
}
- (void)viewDidLoad
{
[super viewDidLoad];
// self.fps = 30;
// Create the AVCaptureSession
AVCaptureSession *session = [[AVCaptureSession alloc] init];
[self setSession:session];
// Setup the preview view
[[self previewView] setSession:session];
// Check for device authorization
[self checkDeviceAuthorizationStatus];
// In general it is not safe to mutate an AVCaptureSession or any of its inputs, outputs, or connections from multiple threads at the same time.
// Why not do all of this on the main queue?
// -[AVCaptureSession startRunning] is a blocking call which can take a long time. We dispatch session setup to the sessionQueue so that the main queue isn't blocked (which keeps the UI responsive).
dispatch_queue_t sessionQueue = dispatch_queue_create("session queue", DISPATCH_QUEUE_SERIAL);
[self setSessionQueue:sessionQueue];
//we will use a separate dispatch session not to block the main queue in processing
dispatch_queue_t im_processingQueue = dispatch_queue_create("im_processing queue", DISPATCH_QUEUE_SERIAL);
[self setIm_processingQueue:im_processingQueue];
dispatch_async(sessionQueue, ^{
[self setBackgroundRecordingID:UIBackgroundTaskInvalid];
NSError *error = nil;
AVCaptureDevice *videoDevice = [AVCamViewController deviceWithMediaType:AVMediaTypeVideo preferringPosition:AVCaptureDevicePositionBack];
AVCaptureDeviceInput *videoDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];
if (error)
{
NSLog(@"%@", error);
}
if ([session canAddInput:videoDeviceInput])
{
[session addInput:videoDeviceInput];
[self setVideoDeviceInput:videoDeviceInput];
dispatch_async(dispatch_get_main_queue(), ^{
// Why are we dispatching this to the main queue?
// Because AVCaptureVideoPreviewLayer is the backing layer for AVCamPreviewView and UIView can only be manipulated on main thread.
// Note: As an exception to the above rule, it is not necessary to serialize video orientation changes on the AVCaptureVideoPreviewLayer’s connection with other session manipulation.
[[(AVCaptureVideoPreviewLayer *)[[self previewView] layer] connection] setVideoOrientation:(AVCaptureVideoOrientation)[self interfaceOrientation]];
});
}
AVCaptureDevice *audioDevice = [[AVCaptureDevice devicesWithMediaType:AVMediaTypeAudio] firstObject];
AVCaptureDeviceInput *audioDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:&error];
if (error)
{
NSLog(@"%@", error);
}
if ([session canAddInput:audioDeviceInput])
{
[session addInput:audioDeviceInput];
}
AVCaptureVideoDataOutput *vid_Output = [[AVCaptureVideoDataOutput alloc] init];
vid_Output.alwaysDiscardsLateVideoFrames = NO;
if ([session canAddOutput:vid_Output])
{
[session addOutput:vid_Output];
AVCaptureConnection *connection = [vid_Output connectionWithMediaType:AVMediaTypeVideo];
if ([connection isVideoStabilizationSupported])
[connection setEnablesVideoStabilizationWhenAvailable:YES];
[self setVid_Output:vid_Output];
}
});
}
- (void)viewWillAppear:(BOOL)animated
{
dispatch_async([self sessionQueue], ^{
[self addObserver:self forKeyPath:@"sessionRunningAndDeviceAuthorized" options:(NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew) context:SessionRunningAndDeviceAuthorizedContext];
[self addObserver:self forKeyPath:@"vid_Output.recording" options:(NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew) context:RecordingContext];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(subjectAreaDidChange:) name:AVCaptureDeviceSubjectAreaDidChangeNotification object:[[self videoDeviceInput] device]];
__weak AVCamViewController *weakSelf = self;
[self setRuntimeErrorHandlingObserver:[[NSNotificationCenter defaultCenter] addObserverForName:AVCaptureSessionRuntimeErrorNotification object:[self session] queue:nil usingBlock:^(NSNotification *note) {
AVCamViewController *strongSelf = weakSelf;
dispatch_async([strongSelf sessionQueue], ^{
// Manually restarting the session since it must have been stopped due to an error.
[[strongSelf session] startRunning];
});
}]];
[[self session] startRunning];
});
}
- (void)viewDidDisappear:(BOOL)animated
{
dispatch_async([self sessionQueue], ^{
[[self session] stopRunning];
[[NSNotificationCenter defaultCenter] removeObserver:self name:AVCaptureDeviceSubjectAreaDidChangeNotification object:[[self videoDeviceInput] device]];
[[NSNotificationCenter defaultCenter] removeObserver:[self runtimeErrorHandlingObserver]];
[self removeObserver:self forKeyPath:@"sessionRunningAndDeviceAuthorized" context:SessionRunningAndDeviceAuthorizedContext];
[self removeObserver:self forKeyPath:@"vid_Output.recording" context:RecordingContext];
});
}
- (BOOL)prefersStatusBarHidden
{
return YES;
}
- (BOOL)shouldAutorotate
{
// Disable autorotation of the interface when recording is in progress.
return ![self lockInterfaceRotation];
}
- (NSUInteger)supportedInterfaceOrientations
{
return UIInterfaceOrientationMaskAll;
}
- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
[[(AVCaptureVideoPreviewLayer *)[[self previewView] layer] connection] setVideoOrientation:(AVCaptureVideoOrientation)toInterfaceOrientation];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if (context == SessionRunningAndDeviceAuthorizedContext)
{
BOOL isRunning = [change[NSKeyValueChangeNewKey] boolValue];
dispatch_async(dispatch_get_main_queue(), ^{
if (isRunning)
{
[[self cameraButton] setEnabled:YES];
}
else
{
[[self cameraButton] setEnabled:NO];
}
});
}
else
{
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
}
}
#pragma mark Actions
- (IBAction)changeCamera:(id)sender {
[[self cameraButton] setEnabled:NO];
dispatch_async([self sessionQueue], ^{
AVCaptureDevice *currentVideoDevice = [[self videoDeviceInput] device];
AVCaptureDevicePosition preferredPosition = AVCaptureDevicePositionUnspecified;
AVCaptureDevicePosition currentPosition = [currentVideoDevice position];
switch (currentPosition)
{
case AVCaptureDevicePositionUnspecified:
preferredPosition = AVCaptureDevicePositionBack;
break;
case AVCaptureDevicePositionBack:
preferredPosition = AVCaptureDevicePositionFront;
break;
case AVCaptureDevicePositionFront:
preferredPosition = AVCaptureDevicePositionBack;
break;
}
AVCaptureDevice *videoDevice = [AVCamViewController deviceWithMediaType:AVMediaTypeVideo preferringPosition:preferredPosition];
AVCaptureDeviceInput *videoDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:nil];
[[self session] beginConfiguration];
[[self session] removeInput:[self videoDeviceInput]];
if ([[self session] canAddInput:videoDeviceInput])
{
[[NSNotificationCenter defaultCenter] removeObserver:self name:AVCaptureDeviceSubjectAreaDidChangeNotification object:currentVideoDevice];
[AVCamViewController setFlashMode:AVCaptureFlashModeAuto forDevice:videoDevice];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(subjectAreaDidChange:) name:AVCaptureDeviceSubjectAreaDidChangeNotification object:videoDevice];
[[self session] addInput:videoDeviceInput];
[self setVideoDeviceInput:videoDeviceInput];
}
else
{
[[self session] addInput:[self videoDeviceInput]];
}
[[self session] commitConfiguration];
dispatch_async(dispatch_get_main_queue(), ^{
[[self cameraButton] setEnabled:YES];
});
});
}
- (IBAction)focusAndExposeTap:(UIGestureRecognizer *)gestureRecognizer
{
CGPoint devicePoint = [(AVCaptureVideoPreviewLayer *)[[self previewView] layer] captureDevicePointOfInterestForPoint:[gestureRecognizer locationInView:[gestureRecognizer view]]];
[self focusWithMode:AVCaptureFocusModeAutoFocus exposeWithMode:AVCaptureExposureModeAutoExpose atDevicePoint:devicePoint monitorSubjectAreaChange:YES];
}
- (void)subjectAreaDidChange:(NSNotification *)notification
{
CGPoint devicePoint = CGPointMake(.5, .5);
[self focusWithMode:AVCaptureFocusModeContinuousAutoFocus exposeWithMode:AVCaptureExposureModeContinuousAutoExposure atDevicePoint:devicePoint monitorSubjectAreaChange:NO];
}
#pragma mark Device Configuration
- (void)focusWithMode:(AVCaptureFocusMode)focusMode exposeWithMode:(AVCaptureExposureMode)exposureMode atDevicePoint:(CGPoint)point monitorSubjectAreaChange:(BOOL)monitorSubjectAreaChange
{
dispatch_async([self sessionQueue], ^{
AVCaptureDevice *device = [[self videoDeviceInput] device];
NSError *error = nil;
if ([device lockForConfiguration:&error])
{
if ([device isFocusPointOfInterestSupported] && [device isFocusModeSupported:focusMode])
{
[device setFocusMode:focusMode];
[device setFocusPointOfInterest:point];
}
if ([device isExposurePointOfInterestSupported] && [device isExposureModeSupported:exposureMode])
{
[device setExposureMode:exposureMode];
[device setExposurePointOfInterest:point];
}
[device setSubjectAreaChangeMonitoringEnabled:monitorSubjectAreaChange];
[device unlockForConfiguration];
}
else
{
NSLog(@"%@", error);
}
});
}
+ (void)setFlashMode:(AVCaptureFlashMode)flashMode forDevice:(AVCaptureDevice *)device
{
if ([device hasFlash] && [device isFlashModeSupported:flashMode])
{
NSError *error = nil;
if ([device lockForConfiguration:&error])
{
[device setFlashMode:flashMode];
[device unlockForConfiguration];
}
else
{
NSLog(@"%@", error);
}
}
}
+ (AVCaptureDevice *)deviceWithMediaType:(NSString *)mediaType preferringPosition:(AVCaptureDevicePosition)position
{
NSArray *devices = [AVCaptureDevice devicesWithMediaType:mediaType];
AVCaptureDevice *captureDevice = [devices firstObject];
for (AVCaptureDevice *device in devices)
{
if ([device position] == position)
{
captureDevice = device;
break;
}
}
return captureDevice;
}
#pragma mark UI
- (void)checkDeviceAuthorizationStatus
{
NSString *mediaType = AVMediaTypeVideo;
[AVCaptureDevice requestAccessForMediaType:mediaType completionHandler:^(BOOL granted) {
if (granted)
{
//Granted access to mediaType
[self setDeviceAuthorized:YES];
}
else
{
//Not granted access to mediaType
dispatch_async(dispatch_get_main_queue(), ^{
[[[UIAlertView alloc] initWithTitle:@"AVCam!"
message:@"AVCam doesn't have permission to use Camera, please change privacy settings"
delegate:self
cancelButtonTitle:@"OK"
otherButtonTitles:nil] show];
[self setDeviceAuthorized:NO];
});
}
}];
}
- (IBAction)gpuButtonPress:(id)sender {
self.cpu_processing = false;
self.gpu_processing = true;
}
- (IBAction)cpuButtonPress:(id)sender {
self.cpu_processing = true;
self.gpu_processing = false;
}
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer
{
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(imageBuffer, 0);
void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
CGImageRef quartzImage = CGBitmapContextCreateImage(context);
CVPixelBufferUnlockBaseAddress(imageBuffer,0);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
int frontCameraImageOrientation = UIImageOrientationLeftMirrored;
//int backCameraImageOrientation = UIImageOrientationRight;
UIImage *image = [UIImage imageWithCGImage:quartzImage scale:(CGFloat)1.0 orientation:frontCameraImageOrientation];
//UIImage *image = [UIImage imageWithCGImage:quartzImage];
CGImageRelease(quartzImage);
return (image);
}
#pragma mark File Output Delegate
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
@autoreleasepool {
dispatch_async([self im_processingQueue], ^{
UIImage *img = [self imageFromSampleBuffer:sampleBuffer];
});
//To get back main thread for UI display
dispatch_async(dispatch_get_main_queue(), ^{
});
}
}
@end