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# VTRAWProcessingParameterChangeHandler

A function the system calls when processing parameters change.

```
typedef void (^)(const struct __CFArray *) VTRAWProcessingParameterChangeHandler;
```

## Parameters

`newParameters`

An array containing the new parameter details.  This follows the same form as the array returned from [`VTRAWProcessingSessionCopyProcessingParameters`](/documentation/VideoToolbox/VTRAWProcessingSessionCopyProcessingParameters).

## Discussion

The system invokes this callback when available parameters or parameter values change without an explicit call to [`VTRAWProcessingSessionSetProcessingParameters`](/documentation/VideoToolbox/VTRAWProcessingSessionSetProcessingParameters). This is intended to allow the client to update any UI driven by these parameters.

---

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