iOS: captureOutput: didOutputSampleBuffer: fromConnection NÃO é chamado
Quero extrair quadros do feed ao vivo do AVCaptureSession e estou usando o AVCam da Apple como um caso de teste. Aqui está o link para AVCam:
https://developer.apple.com/library/ios/samplecode/AVCam/Introduction/Intro.html
Eu descobri quecaptureOutput:didOutputSampleBuffer:fromConnection
NÃO é chamado e eu gostaria de saber por que ou o que estou fazendo de errado.
Aqui está o que eu fiz:
(1) eu faço oAVCamViewController
um delegado
@interface AVCamViewController () <AVCaptureFileOutputRecordingDelegate, AVCaptureVideoDataOutputSampleBufferDelegate>
(2) eu criei umAVCaptureVideoDataOutput
objeto e adicione-o à sessão
AVCaptureVideoDataOutput *videoDataOutput = [[AVCaptureVideoDataOutput alloc] init];
if ([session canAddOutput:videoDataOutput])
{
[session addOutput:videoDataOutput];
}
(3) Adicionei o método delegado e teste registrando uma sequência aleatória para testar
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
NSLog(@"I am called");
}
O aplicativo de teste funciona, mas captureOutput: didOutputSampleBuffer: fromConnection não é chamado.
(4) Li no SO que a variável de sessão emAVCaptureSession *session = [[AVCaptureSession alloc] init];
ser local em viewDidLoad é uma possível razão pela qual o delegado não é chamado e eu a tornei uma variável de instância da classe AVCamViewController, mas não é chamada.
Aqui está o método viewDidLoad com o qual estou testando (extraído da AVCam), adicionei o AVCaptureDataOutput no final do método:
- (void)viewDidLoad
{
[super viewDidLoad];
// Create the 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];
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];
}
AVCaptureMovieFileOutput *movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];
if ([session canAddOutput:movieFileOutput])
{
[session addOutput:movieFileOutput];
AVCaptureConnection *connection = [movieFileOutput connectionWithMediaType:AVMediaTypeVideo];
if ([connection isVideoStabilizationSupported])
[connection setEnablesVideoStabilizationWhenAvailable:YES];
[self setMovieFileOutput:movieFileOutput];
}
AVCaptureStillImageOutput *stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
if ([session canAddOutput:stillImageOutput])
{
[stillImageOutput setOutputSettings:@{AVVideoCodecKey : AVVideoCodecJPEG}];
[session addOutput:stillImageOutput];
[self setStillImageOutput:stillImageOutput];
}
AVCaptureVideoDataOutput *videoDataOutput = [[AVCaptureVideoDataOutput alloc] init];
[videoDataOutput setSampleBufferDelegate:self queue:sessionQueue];
if ([session canAddOutput:videoDataOutput])
{
NSLog(@"Yes I can add it");
[session addOutput:videoDataOutput];
}
});
}
- (void)viewWillAppear:(BOOL)animated
{
dispatch_async([self sessionQueue], ^{
[self addObserver:self forKeyPath:@"sessionRunningAndDeviceAuthorized" options:(NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew) context:SessionRunningAndDeviceAuthorizedContext];
[self addObserver:self forKeyPath:@"stillImageOutput.capturingStillImage" options:(NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew) context:CapturingStillImageContext];
[self addObserver:self forKeyPath:@"movieFileOutput.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];
[[strongSelf recordButton] setTitle:NSLocalizedString(@"Record", @"Recording button record title") forState:UIControlStateNormal];
});
}]];
[[self session] startRunning];
});
}
Alguém pode me dizer por que e sugestões sobre como corrigi-lo?