---
title: kAudioFilePropertyReserveDuration
framework: audiotoolbox
role: symbol
role_heading: Global Variable
path: audiotoolbox/kaudiofilepropertyreserveduration
---

# kAudioFilePropertyReserveDuration

The duration in seconds of the data expected to be written. Set this property before any data has been written to reserve space in the file header for a packet table and other information to appear before the audio data. Otherwise, the packet table might get written at the end of the file, preventing the file from being streamable.

## Declaration

```swift
var kAudioFilePropertyReserveDuration: AudioFilePropertyID { get }
```

## See Also

### Constants

- [kAudioFilePropertyFileFormat](audiotoolbox/kaudiofilepropertyfileformat.md)
- [kAudioFilePropertyDataFormat](audiotoolbox/kaudiofilepropertydataformat.md)
- [kAudioFilePropertyFormatList](audiotoolbox/kaudiofilepropertyformatlist.md)
- [kAudioFilePropertyIsOptimized](audiotoolbox/kaudiofilepropertyisoptimized.md)
- [kAudioFilePropertyMagicCookieData](audiotoolbox/kaudiofilepropertymagiccookiedata.md)
- [kAudioFilePropertyAudioDataByteCount](audiotoolbox/kaudiofilepropertyaudiodatabytecount.md)
- [kAudioFilePropertyAudioDataPacketCount](audiotoolbox/kaudiofilepropertyaudiodatapacketcount.md)
- [kAudioFilePropertyMaximumPacketSize](audiotoolbox/kaudiofilepropertymaximumpacketsize.md)
- [kAudioFilePropertyDataOffset](audiotoolbox/kaudiofilepropertydataoffset.md)
- [kAudioFilePropertyChannelLayout](audiotoolbox/kaudiofilepropertychannellayout.md)
- [kAudioFilePropertyDeferSizeUpdates](audiotoolbox/kaudiofilepropertydefersizeupdates.md)
- [kAudioFilePropertyDataFormatName](audiotoolbox/kaudiofilepropertydataformatname.md)
- [kAudioFilePropertyMarkerList](audiotoolbox/kaudiofilepropertymarkerlist.md)
- [kAudioFilePropertyRegionList](audiotoolbox/kaudiofilepropertyregionlist.md)
- [kAudioFilePropertyPacketToFrame](audiotoolbox/kaudiofilepropertypackettoframe.md)