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# renderContextObserver

The block that the system calls when the rendering context changes.

```
@property (nonatomic, readonly) AURenderContextObserver renderContextObserver;
```

## Discussion

Implement this property if your Audio Unit creates auxilliary realtime rendering threads. Return a block for the system to call when the rendering context changes.

> Important:
> The block you provide is for system use only. Audio Unit hosts must not attempt to interact with the audio unit through this block.

---

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