canSetSessionPreset：AVCaptureSessionPreset1920x1080在iOS4中导致“访问错误”

Question

Here is my code:

if( [self.captureSession canSetSessionPreset:AVCaptureSessionPreset1920x1080] == YES )
    {
    [self.captureSession setSessionPreset:AVCaptureSessionPreset1920x1080];
    self.currentPreset = GMCVideoCaptureRecordingPresetFullHD;
    }

On iOS4 execution stops on the first line with 'Bad access' error. On iOS5 it works fine.

How to correctly check for compatibility here?

Answer 1

AVCaptureSessionPreset1920x1080 is an NSString *const . You can just check that its address is not NULL . So like so:

if( &AVCaptureSessionPreset1920x1080 != NULL && [self.captureSession canSetSessionPreset:AVCaptureSessionPreset1920x1080] == YES )
{
    [self.captureSession setSessionPreset:AVCaptureSessionPreset1920x1080];
    self.currentPreset = GMCVideoCaptureRecordingPresetFullHD;
}

That should do what you want. Note that you won't be setting the preset on < iOS 5 though so you will presumably want an else in there to handle the case of it being < iOS 5 or the 1920x1080 preset can't be set.