# AVAssetReaderSampleReferenceOutput An object that reads sample references from an asset track. ``` class AVAssetReaderSampleReferenceOutput ``` ## Overview Apps can extract information about the location of samples in a track — the file URL and offset — by adding an instance of this class to an asset reader. Read the and attachments on the extracted sample buffers to get the location of the sample data. You can also append sample buffers that you extract using this class to an [`AVAssetWriterInput`](/documentation/AVFoundation/AVAssetWriterInput) instance to create movie tracks that aren’t self-contained and reference data in the original file instead. To write tracks that aren’t self-contained, use instances of [`AVAssetWriter`](/documentation/AVFoundation/AVAssetWriter) that you configure to write files of type [`mov`](/documentation/AVFoundation/AVFileType/mov). Because this output doesn’t return sample data, it ignores the value of the [`alwaysCopiesSampleData`](/documentation/AVFoundation/AVAssetReaderOutput/alwaysCopiesSampleData) property. ## Topics ### Creating a sample reference output [`assetReaderSampleReferenceOutputWithTrack:`](/documentation/AVFoundation/AVAssetReaderSampleReferenceOutput/assetReaderSampleReferenceOutputWithTrack:) Returns a new object that supplies sample references. [`init(track:)`](/documentation/AVFoundation/AVAssetReaderSampleReferenceOutput/init(track:)) Creates an object that supplies sample references. ### Inspecting the track [`track`](/documentation/AVFoundation/AVAssetReaderSampleReferenceOutput/track) The track from which the output reads sample references. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)