yes, i don't know why. but AVSampleBufferDisplayLayer can render in the background, i am very curious about this.

In iOS 14 system, I can do it in the picture in picture. but when I do something in iOS 15.0 system, the render output the error (kIOGPUCommandBufferCallbackErrorBackgroundExecutionNotPermitted), how can i do?

Yes, I try to render while my app is in the picture in picture (The app is in the background).