Continuous capture image with AVFoudation in iPhone

Now, I can capture an image using avfoundation , like below. But how should I do to capture images (e.g. 20 or 30 images开发者_JAVA技巧) continuously?

[stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error)
 {
     CFDictionaryRef exifAttachments = CMGetAttachment( imageSampleBuffer, kCGImagePropertyExifDictionary, NULL);
     if (exifAttachments)
     {
         // Do something with the attachments.
         NSLog(@"attachements: %@", exifAttachments);
     }
     else
         NSLog(@"no attachments");

     NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
     UIImage *image = [[UIImage alloc] initWithData:imageData];

     // use the image

 }];

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Whoops, I forgot to follow up on your comment:

The scenario you describe would most easily be solved by using some sort of timer.
Depending on what level of accuracy you need, there are different candidates to look for:

1. A repeating NSTimer is pretty easy and straight-forward to use. As this class works in conjunction with runloops, there are some pitfalls to be aware of — one being, that the accuracy is limited (but for what you seemingly want to accomplish, that should not be a problem at all).
2. If you need a little more accuracy in the long run, you can still use NSTimer: Use initWithFireDate:… with repeats:NO and create a new timer this way, (using a date relative to the supposed fireDate of the old one) when the old one fires.
3. If you really need a high degree of accuracy, you should have a look into dispatch timers. They are a part of GCD and, thus, a pretty low-level tech. If you decide to follow this path for accuracy, you should probably use your own dispatch queue in the call to dispatch_source_create.

In any case, your code for snapping the picture goes into the respective handler.