Changing Metadata RectOfInterest causes pause

Number:rdar://18980982 Date Originated:14 Nov 2014
Status:Open Resolved:
Product:iOS Product Version:8.1
Classification:Serious Bug Reproducible:Always
In a barcode scanning scenario with a running AVCapture session: if you adjust the metadata rectOfInterest the preview video goes blank and the main thread is blocked for a noticeable delay.

Steps to Reproduce:
1. Create a barcode scanner app with a preview layer
2. hook up the metadata objects detector and delegate
3. on interface rotation, adjust the rect of interest
4. run the app in portrait, rotate to landscape

Expected Results:
There should be no noticeable visual effect of changing the rect of interest

Actual Results:
- The preview video goes blank
- The main thread is blocked
- After this noticeable delay the interface rotates

iOS 8.1

My workaround is to not change the rect of interest, but instead check if reported metadata objects' bounds are within my scan target view area.

This is quite suboptimal since changing the rect of interest (in particular for 1D barcodes) would be very beneficial for the scanning performance due to scan lines being used. The smaller the area, the more compact they can be.

iPhone 6+



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