# copyNextSampleBuffer() Copies the next sample buffer from the output. ``` func copyNextSampleBuffer() -> CMSampleBuffer? ``` ## Return Value The output sample buffer, or `nil` if you’ve read all samples or an error occurs. ## Discussion This method returns `nil` when you’ve read all available sample buffers, or if there’s an error. Check the value of the asset reader’s [`status`](/documentation/AVFoundation/AVAssetReader/status-swift.property) property to determine the reason. The order of returned sample buffers depends on the output’s configuration. For a track output with a `nil` [`outputSettings`](/documentation/AVFoundation/AVAssetReaderTrackOutput/outputSettings) dictionary, the output skips decoding and returns sample buffers in decode order. Preserve that order when working with the encoded samples directly, such as when passing them to [`AVAssetWriter`](/documentation/AVFoundation/AVAssetWriter). When the output decodes the samples, it returns them in presentation order. Playback and downstream processing operate in presentation order, so decode order no longer matters after decoding. --- 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)