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# VTRAWProcessingSessionSetParameterChangedHandler

```
extern OSStatus VTRAWProcessingSessionSetParameterChangedHandler(VTRAWProcessingSessionRef session, VTRAWProcessingParameterChangeHandler parameterChangeHandler);
```

## Parameters

`session`

The RAW processing session.

`parameterChangeHandler`

A VTRAWProcessingParameterChangeHandler block which will be called when the set of processing parameters changes, or the value of a parameter changes without the client explicitly requesting it.
Setting this to NULL removes the current handler.

## Discussion

\abstract Provides a block which will be called when the VTRAWProcessingPlugin changes the set of processing parameters..
\discussion This block will be called the VTRAWProcessingPlugin either changes the set of available processing parameters, or changes the current value of parameters.
The VTRAWProcessingPlugin may change parameters based on metadata associated with input frames, or in response to other parameters configured by VTRAWProcessingSessionSetProcessingParameters.
This optional and does not need to be configured if the client is not driving UI based on these parameters, or otherwise does not need this.

---

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