# preferredMediaChunkSize The maximum size to use for each chunk of sample data written to the file for file types that support media chunk duration. ``` var preferredMediaChunkSize: Int { get set } ``` ## Discussion The total size of the samples in a chunk can be no greater than the preferred chunk size, or the size of a single sample if the single sample’s size is greater than the preferred chunk size. The default media chunk duration is `1024 * 1024` bytes. Setting a negative value for the chunk duration will cause an error. A larger chunk size can result in fewer reads from the storage container, at the potential expense of a larger memory footprint. --- 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)