You are calling some UIKit methods on a different thread. UIKit mostly can be used only from the main thread. You've got a NSURLSession that runs a callback on a background thread and then calls UIKit. The main thread checker is useful to catch this kind of issues.

The issue was triggered by thread 36, but you didn't post the stack trace of that thread, so it's not possible to know what's going wrong.

Of course, VideoToolbox will create encoded data with the specification of the format you selected. It will be decodable on every other hardware.

Video range means that black is 16 and white is 235, then there are super black and super white, that were historically useful when you had to color correct the video and restore missing details because the image exposure was not the best one. How are you converting from YpCbCr to RGB and back? Are you converting back to limited range or to full range.

The executable is trying to load some unsigned libraries from /usr/local/opt/, that can't be loaded because it was signed with the hardened runtime enabled. Maybe there is a way to do a static build with that library included? I never used gfortran, so I can't help more than this.

It seems the C version is called CMTaggedBufferGroup.

Maybe you need an autorelease pool.

User defaults are cached, so if you want to remove them and clear the cache use the defaults cli command.

https://developer.apple.com/documentation/quartzcore/cametallayer

The correct way is to show an NSOpenPanel and ask the user to open the Desktop folder. Then store the security scoped bookmark.

Calling a method on an object that has no implementation of that method should generate an exception, that should be printed in the log when running inside Xcode. Or you could override NSApplication - (void)reportException:(NSException *)exception and handle it on your own.

Keep an array somewhere with all the windows you've created, and get them from this array.

NSDictionary doesn't make any guarantee about order, it's a data structure that is not meant to be ordered, so it's not a surprise the result looks like that. There is a NSJSONWritingSortedKeys option if you want things in lexicographic order when converting from NSObjects to json. If not you will have to use an NSArray.

When in doubt, check the framework header directly, you can find the one you want in /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks/MediaToolbox.framework/Versions/A/Headers/MTProfessionalVideoWorkflow.h

From my experience, VideoToolbox dictionaries are often incomplete or wrong. Anyway, yes, H.264 and HEVC encoders and others are always hardware accelerated on iOS.