ios capturing image using AVFramework

Question

I\'m capturing images using this code

#pragma mark - image capture

// Create and configure a capture session and start it running
- (void)setupCaptureSessio         


        

Answer 1

Be careful - callback from AVCaptureOutput is posted in dispatch queue you specified. I saw you perform UI updates from this callback, and that is wrong. You should perform them only in main queue. E.g.

- (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 2

And here is a Swift version of imageFromSampleBuffer function:

func imageFromSampleBuffer(sampleBuffer:CMSampleBuffer!) -> UIImage {
    let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!
    CVPixelBufferLockBaseAddress(imageBuffer, 0)

    let baseAddress = CVPixelBufferGetBaseAddress(imageBuffer)
    let bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer)
    let width = CVPixelBufferGetWidth(imageBuffer)
    let height = CVPixelBufferGetHeight(imageBuffer)

    let colorSpace = CGColorSpaceCreateDeviceRGB()

    let bitmapInfo:CGBitmapInfo = [.ByteOrder32Little, CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawValue)]
    let context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, bitmapInfo.rawValue)

    let quartzImage = CGBitmapContextCreateImage(context)
    CVPixelBufferUnlockBaseAddress(imageBuffer, 0)

    let image = UIImage(CGImage: quartzImage!)
    return image
}

Above working for me with following video settings:

videoDataOutput = AVCaptureVideoDataOutput()
videoDataOutput?.videoSettings = [kCVPixelBufferPixelFormatTypeKey:Int(kCVPixelFormatType_32BGRA)]
            videoDataOutput?.setSampleBufferDelegate(self, queue: queue)

Answer 3

Add the following line

output.minFrameDuration = CMTimeMake(5, 1);

below the comment

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

but above the

[session startRunning];

Edit

Use the following code to preview the camera output.

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 fine..

Apple has provided a way to set the minFrameDuration here

So now, use the following code to set the frame duration

AVCaptureConnection *conn = [output connectionWithMediaType:AVMediaTypeVideo];

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