How can I ensure that my AVCaptureSession has enough time to run?

Question

I need to ensure that my AVCaptureSession runs for 15 seconds before being stopped. How could I go about doing this? I'm hesitant about using wait or sleep because I'm fairly sure that it would halt the intake of input. What can I use to wait 15 seconds before I run the stop command?

Sample code:

[self.session startRunning];
// wait 15 seconds 
[self.session stopRunning];

score 1 · Accepted Answer · answered Dec 27 '16 at 23:52

1

Sleep would indeed bring everything to a screeching halt. Don't do that.

You could use a call to dispatch_after:

[self.session startRunning];
// wait 15 seconds 
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 
  15 * NSEC_PER_SEC), 
  dispatch_get_main_queue(), ^{
    [self.session stopRunning]; 
});

Another alternative would be to set up a CADisplayLink and test to see if 15 seconds has elapsed on each call, but the above should be fine unless you need millisecond accuracy.

answered Dec 27 '16 at 23:52

Duncan C

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I tried this, but while debugging, the compiler still immediately goes to the stopRunning line. – fi12 Dec 28 '16 at 01:56
Why do you think it does that? – Duncan C Dec 28 '16 at 03:06
I don't know, have you any ideas? – fi12 Dec 28 '16 at 03:08
Never mind, I've actually figured it out. I just reimplemented your code and it worked as expected. Thanks for the help! – fi12 Jan 02 '17 at 23:30

How can I ensure that my AVCaptureSession has enough time to run?

1 Answers1