---
title: activeFormatIndex
framework: coremediaio
role: symbol
role_heading: Instance Property
path: coremediaio/cmioextensionstreamproperties/activeformatindex-83u7z
---

# activeFormatIndex

The index of the active format.

## Declaration

```swift
@nonobjc var activeFormatIndex: Int? { get set }
```

## Discussion

Discussion This value represents the index of the active format in the source’s formats array. The key for this property is streamActiveFormatIndex.

## See Also

### Configuring Source Properties

- [frameDuration](coremediaio/cmioextensionstreamproperties/frameduration-4rnl9.md)
- [maxFrameDuration](coremediaio/cmioextensionstreamproperties/maxframeduration-5qqg.md)