---
title: kVTCompressionPropertyKey_EnableLTR
framework: videotoolbox
role: symbol
role_heading: Global Variable
path: videotoolbox/kvtcompressionpropertykey_enableltr
---

# kVTCompressionPropertyKey_EnableLTR

Enables Long Term Reference (LTR) frames during encoding.

## Declaration

```swift
let kVTCompressionPropertyKey_EnableLTR: CFString
```

## See Also

### Long-Term Reference

- [kVTEncodeFrameOptionKey_AcknowledgedLTRTokens](videotoolbox/kvtencodeframeoptionkey_acknowledgedltrtokens.md)
- [kVTEncodeFrameOptionKey_ForceLTRRefresh](videotoolbox/kvtencodeframeoptionkey_forceltrrefresh.md)
- [kVTSampleAttachmentKey_RequireLTRAcknowledgementToken](videotoolbox/kvtsampleattachmentkey_requireltracknowledgementtoken.md)