Reduce the area in which barcodes are detected and decoded is useful if multiple barcodes are present in the same image. In other cases, it is better to have the full image detection enabled, as it has more advantages.
//Restrict scanning area
scanSettings.restrictedAreaScanningEnabled = true;
//Reduce the active area
CGRect activeScanArea = CGRectMake(0.0f, 0.5f, 1.0f, 0.04f);