---
title: kVTSampleAttachmentKey_RequireLTRAcknowledgementToken
framework: videotoolbox
role: symbol
role_heading: Global Variable
path: videotoolbox/kvtsampleattachmentkey_requireltracknowledgementtoken
---

# kVTSampleAttachmentKey_RequireLTRAcknowledgementToken

A number value that contains a unique token for this Long Term Reference (LTR).

## Declaration

```swift
let kVTSampleAttachmentKey_RequireLTRAcknowledgementToken: CFString
```

## See Also

### Long-Term Reference

- [kVTCompressionPropertyKey_EnableLTR](videotoolbox/kvtcompressionpropertykey_enableltr.md)
- [kVTEncodeFrameOptionKey_AcknowledgedLTRTokens](videotoolbox/kvtencodeframeoptionkey_acknowledgedltrtokens.md)
- [kVTEncodeFrameOptionKey_ForceLTRRefresh](videotoolbox/kvtencodeframeoptionkey_forceltrrefresh.md)