---
title: copyFormatDescription()
framework: avfoundation
role: symbol
role_heading: Instance Method
path: avfoundation/avtimedmetadatagroup/copyformatdescription()
---

# copyFormatDescription()

Creates a format description based on the receiver’s items.

## Declaration

```swift
func copyFormatDescription() -> CMMetadataFormatDescription?
```

## Return Value

Return Value An instance of CMMetadataFormatDescription sufficient to describe the contents of all the items referenced by the object.

## Discussion

Discussion The returned format description is suitable for use as the format hint parameter when creating an instance of AVAssetWriterInput. Each item referenced by the receiver must carry a non-nil value for its dataType property.  An exception will be thrown if any item does not have a data type.