---
title: kCMSampleBufferAttachmentKey_TransitionID
framework: coremedia
role: symbol
role_heading: Global Variable
path: coremedia/kcmsamplebufferattachmentkey_transitionid
---

# kCMSampleBufferAttachmentKey_TransitionID

Marks a transition from one source of buffers to another.

## Declaration

```swift
let kCMSampleBufferAttachmentKey_TransitionID: CFString
```

## Discussion

Discussion For example, during gapless playback of a list of songs, this attachment marks the first buffer from the next song.        If this attachment is on a buffer containing no samples, the first following buffer that contains samples is the        buffer that contains the first samples from the next song.  The value of this attachment is a CFTypeRef.  This        transition identifier should be unique within a playlist, so each transition in a playlist is uniquely        identifiable.  A CFNumber counter that increments with each transition is a simple example.

## See Also

### Sample Buffer Keys

- [kCMSampleBufferAttachmentKey_DisplayEmptyMediaImmediately](coremedia/kcmsamplebufferattachmentkey_displayemptymediaimmediately.md)
- [kCMSampleBufferAttachmentKey_DrainAfterDecoding](coremedia/kcmsamplebufferattachmentkey_drainafterdecoding.md)
- [kCMSampleBufferAttachmentKey_DroppedFrameReason](coremedia/kcmsamplebufferattachmentkey_droppedframereason.md)
- [kCMSampleBufferDroppedFrameReason_FrameWasLate](coremedia/kcmsamplebufferdroppedframereason_framewaslate.md)
- [kCMSampleBufferDroppedFrameReason_OutOfBuffers](coremedia/kcmsamplebufferdroppedframereason_outofbuffers.md)
- [kCMSampleBufferDroppedFrameReason_Discontinuity](coremedia/kcmsamplebufferdroppedframereason_discontinuity.md)
- [kCMSampleBufferAttachmentKey_DroppedFrameReasonInfo](coremedia/kcmsamplebufferattachmentkey_droppedframereasoninfo.md)
- [kCMSampleBufferDroppedFrameReasonInfo_CameraModeSwitch](coremedia/kcmsamplebufferdroppedframereasoninfo_cameramodeswitch.md)
- [kCMSampleBufferAttachmentKey_EmptyMedia](coremedia/kcmsamplebufferattachmentkey_emptymedia.md)
- [kCMSampleBufferAttachmentKey_EndsPreviousSampleDuration](coremedia/kcmsamplebufferattachmentkey_endsprevioussampleduration.md)
- [kCMSampleBufferAttachmentKey_FillDiscontinuitiesWithSilence](coremedia/kcmsamplebufferattachmentkey_filldiscontinuitieswithsilence.md)
- [kCMSampleBufferAttachmentKey_ForceKeyFrame](coremedia/kcmsamplebufferattachmentkey_forcekeyframe.md)
- [kCMSampleBufferAttachmentKey_GradualDecoderRefresh](coremedia/kcmsamplebufferattachmentkey_gradualdecoderrefresh.md)
- [kCMSampleBufferAttachmentKey_PermanentEmptyMedia](coremedia/kcmsamplebufferattachmentkey_permanentemptymedia.md)
- [kCMSampleBufferAttachmentKey_PostNotificationWhenConsumed](coremedia/kcmsamplebufferattachmentkey_postnotificationwhenconsumed.md)