Unfortunately the crackle in audio on certain video tracks which have been been added to iTunes / TV library which was introduced in iPadOS 14.5, iOS 14.5, tvOS 14.5 & macOS 11.3 is still present in iPadOS 15. Unfortunately I am unable to check on iOS and macOS as I am down to daily drivers which are compatible right now and my only downgradable tvOS device can't be restored to a working version of tvOS 14