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# VTDecompressionSessionSetMultiImageCallback

Provides a callback capable of receiving multiple images for individual frame decoding requests.

```
extern OSStatus VTDecompressionSessionSetMultiImageCallback(VTDecompressionSessionRef decompressionSession, VTDecompressionOutputMultiImageCallback outputMultiImageCallback, void *outputMultiImageRefcon);
```

## Parameters

`decompressionSession`

The decompression session.

`outputMultiImageCallback`

A callback to handle multi-image output.

`outputMultiImageRefcon`

Your reference value for the session.

## Return Value

An `OSStatus` value that indicates the result of the operation.

## Discussion

In multi-image decompression, a single video sample contains a single frame (with one PTS) that the system decodes to produce multiple images.

The system uses the multi-image callback when the video decoder outputs <doc://com.apple.documentation/documentation/CoreMedia/CMTaggedBufferGroupRef> objects, or when frame decoding fails and returns a nonzero status. The original single-image callback is only used in the case where the video decoder outputs a <doc://com.apple.documentation/documentation/CoreVideo/CVImageBuffer> instead of a <doc://com.apple.documentation/documentation/CoreMedia/CMTaggedBufferGroupRef>.

## Topics

### Output Callback

[`VTDecompressionOutputMultiImageCallback`](/documentation/VideoToolbox/VTDecompressionOutputMultiImageCallback)

A callback that the system invokes when multi-image frame decompression completes.


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