Capture d'image avec AVFramework

Question

Je capture des images en utilisant ce code

 #pragma mark - image capture

// Create and configure a capture session and start it running
- (void)setupCaptureSession 
{
    NSError *error = nil;

    // Create the session
    AVCaptureSession *session = [[AVCaptureSession alloc] init];

    // Configure the session to produce lower resolution video frames, if your 
    // processing algorithm can cope. We'll specify medium quality for the
    // chosen device.
    session.sessionPreset = AVCaptureSessionPresetMedium;

    // Find a suitable AVCaptureDevice
    AVCaptureDevice *device = [AVCaptureDevice
                           defaultDeviceWithMediaType:AVMediaTypeVideo];

    // Create a device input with the device and add it to the session.
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device 
                                                                    error:&error];
    if (!input)
    {
        NSLog(@"PANIC: no media input");
    }
    [session addInput:input];

    // Create a VideoDataOutput and add it to the session
    AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
    [session addOutput:output];

    // Configure your output.
    dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
    [output setSampleBufferDelegate:self queue:queue];
    dispatch_release(queue);

    // Specify the pixel format
    output.videoSettings = 
    [NSDictionary dictionaryWithObject:
    [NSNumber numberWithInt:kCVPixelFormatType_32BGRA] 
                            forKey:(id)kCVPixelBufferPixelFormatTypeKey];


    // If you wish to cap the frame rate to a known value, such as 15 fps, set 
    // minFrameDuration.

    // Start the session running to start the flow of data
    [session startRunning];

    // Assign session to an ivar.
    [self setSession:session];
}




// Delegate routine that is called when a sample buffer was written
- (void)captureOutput:(AVCaptureOutput *)captureOutput 
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer 
   fromConnection:(AVCaptureConnection *)connection
{ 
    NSLog(@"captureOutput: didOutputSampleBufferFromConnection");

    // Create a UIImage from the sample buffer data
    UIImage *image = [self imageFromSampleBuffer:sampleBuffer];

    //< Add your code here that uses the image >
    [self.imageView setImage:image];
    [self.view setNeedsDisplay];
}


// Create a UIImage from sample buffer data
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer 
{
    NSLog(@"imageFromSampleBuffer: called");
    // Get a CMSampleBuffer's Core Video image buffer for the media data
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); 
    // Lock the base address of the pixel buffer
    CVPixelBufferLockBaseAddress(imageBuffer, 0); 

    // Get the number of bytes per row for the pixel buffer
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer); 

    // Get the number of bytes per row for the pixel buffer
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer); 
    // Get the pixel buffer width and height
    size_t width = CVPixelBufferGetWidth(imageBuffer); 
    size_t height = CVPixelBufferGetHeight(imageBuffer); 

    // Create a device-dependent RGB color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 

    // Create a bitmap graphics context with the sample buffer data
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, 
                                             bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst); 
    // Create a Quartz image from the pixel data in the bitmap graphics context
    CGImageRef quartzImage = CGBitmapContextCreateImage(context); 
    // Unlock the pixel buffer
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);


    // Free up the context and color space
    CGContextRelease(context); 
    CGColorSpaceRelease(colorSpace);

    // Create an image object from the Quartz image
    UIImage *image = [UIImage imageWithCGImage:quartzImage];

    // Release the Quartz image
    CGImageRelease(quartzImage);

    return (image);
}

-(void)setSession:(AVCaptureSession *)session
{
    NSLog(@"setting session...");
    self.captureSession=session;
}
 

La capture de code fonctionne. Mais! J'ai besoin de changer les choses: - flux vidéo de la caméra à mon avis. - obtenir des images toutes les (par exemple 5 secondes). Aidez-moi s'il vous plaît, comment cela peut-il être fait?

Answer 1

Ajoutez la ligne suivante

output.minFrameDuration = CMTimeMake(5, 1);

ci-dessous le commentaire

 // If you wish to cap the frame rate to a known value, such as 15 fps, set
 // minFrameDuration.

mais au-dessus de la

[session startRunning];

Modifier

Utilisez le code suivant pour afficher l'aperçu de la sortie de la caméra.

AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session];
UIView *aView = self.view;
CGRect videoRect = CGRectMake(0.0, 0.0, 320.0, 150.0);
previewLayer.frame = videoRect; // Assume you want the preview layer to fill the view.
[aView.layer addSublayer:previewLayer];

Edit 2: Ok bien..

Apple a fourni un moyen de définir la minFrameDuration ici

Donc, maintenant, utilisez le code suivant pour définir la durée d'affichage des images

AVCaptureConnection *conn = [output connectionWithMediaType:AVMediaTypeVideo];

if (conn.supportsVideoMinFrameDuration)
    conn.videoMinFrameDuration = CMTimeMake(5,1);
if (conn.supportsVideoMaxFrameDuration)
    conn.videoMaxFrameDuration = CMTimeMake(5,1);

Answer 2

Faites attention - le rappel d'AVCaptureOutput est envoyé dans la file d'attente de distribution que vous avez spécifiée. Je vous ai vu effectuer des mises à jour de l'interface utilisateur à partir de ce rappel, ce qui est faux. Vous devriez les exécuter uniquement en file d'attente principale. Par exemple

     - (void)captureOutput:(AVCaptureOutput *)captureOutput 
    didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer 
       fromConnection:(AVCaptureConnection *)connection
    { 
        NSLog(@"captureOutput: didOutputSampleBufferFromConnection");

        // Create a UIImage from the sample buffer data
        UIImage *image = [self imageFromSampleBuffer:sampleBuffer];
        dispatch_async(dispatch_get_main_queue(), ^{
        //< Add your code here that uses the image >
            [self.imageView setImage:image];
            [self.view setNeedsDisplay];
        }
    } 
 

Answer 3

Le problème d'orientation est lié à la caméra frontale, alors vérifiez le type de périphérique et générez une nouvelle image, cela résoudra définitivement le problème d'orientation:

 -(void)capture:(void(^)(UIImage *))handler{

AVCaptureConnection *videoConnection = nil;
for (AVCaptureConnection *connection in self.stillImageOutput.connections)
{
    for (AVCaptureInputPort *port in [connection inputPorts])
    {
        if ([[port mediaType] isEqual:AVMediaTypeVideo] )
        {
            videoConnection = connection;
            break;
        }
    }
    if (videoConnection) { break; }
}

[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error) {

    if (imageSampleBuffer != NULL) {
        NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
        **UIImage *capturedImage = [UIImage imageWithData:imageData];
        if (self.captureDevice == [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo][1]) {
            capturedImage = [[UIImage alloc] initWithCGImage:capturedImage.CGImage scale:1.0f orientation:UIImageOrientationLeftMirrored];
        }**

        handler(capturedImage);
    }
}];
 

}