Adds a recording observer for a single parameter or all parameters in a group.
- iOS 10.0+
- macOS 10.12+
- tvOS 10.0+
A block called to record parameter changes.
A host can use a recording observer to capture a series of changes to a parameter value as generated by a UI gesture. Unlike a non-recording observer, these callbacks are not throttled.
This block is called in an arbitrary thread context and it is responsible for thread-safety. It must not make any calls to add or remove other observers, including itself, as this will deadlock.