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# kCMSampleAttachmentKey_NotSync

Indicates whether the sample is a sync sample (type `CFBoolean`, default false).

```
let kCMSampleAttachmentKey_NotSync: CFString
```

## Discussion

A sync sample, also known as a key frame or IDR (Instantaneous Decoding Refresh), can be decoded without requiring any previous samples to have been decoded. Samples following a sync sample also do not require samples prior to the sync sample to have been decoded. Samples are assumed to be sync samples by default — set the value for this key to <doc://com.apple.documentation/documentation/CoreFoundation/kCFBooleanTrue> for samples which should not be treated as sync samples.

This attachment is read from and written to media files.

---

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