---
title: kCMSampleBufferAttachmentKey_SampleReferenceByteOffset
framework: coremedia
role: symbol
role_heading: Global Variable
path: coremedia/kcmsamplebufferattachmentkey_samplereferencebyteoffset
---

# kCMSampleBufferAttachmentKey_SampleReferenceByteOffset

Indicates the byte offset at which the sample data begins (type CFNumber).

## Declaration

```swift
let kCMSampleBufferAttachmentKey_SampleReferenceByteOffset: CFString
```

## Discussion

Discussion This key is only used for sample buffers representing sample references. Its value is the byte offset from the beginning of data at the referenced URL to the contiguous sample data.

## 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)