Informs the delegate when the output has started writing to a file.
- iOS 4.0+
- macOS 10.7+
- Mac Catalyst 13.0+
The capture file output that started writing the file.
The file URL of the file that is being written.
An array of
AVCaptureobjects attached to the file output that provided the data that is being written to the file.
If an error condition prevents any data from being written, this method may not be called.
capture are always called, even if no data is written.
You should not assume that this method will be called on a specific thread, and should make this method as efficient as possible.