# currentPassDescription An object that describes the requirements for the current pass. ``` var currentPassDescription: AVAssetWriterInputPassDescription? { get } ``` ## Discussion If the value of this property is `nil`, call the asset writer input’s [`markAsFinished()`](/documentation/AVFoundation/AVAssetWriterInput/markAsFinished()) method because there are no more requests to fulfill. During the first pass, the request contains a single time range value, from zero to positive infinity, that indicates to append all media from the source. This condition is also true when [`canPerformMultiplePasses`](/documentation/AVFoundation/AVAssetWriterInput/canPerformMultiplePasses) is , in which case the asset writer only performs a single pass. The value of this property is `nil` before you call [`startWriting()`](/documentation/AVFoundation/AVAssetWriter/startWriting()) on the containing asset writer. It transitions to an initial non-`nil` value during the call to [`startWriting()`](/documentation/AVFoundation/AVAssetWriter/startWriting()), and changes only after a call to [`markCurrentPassAsFinished()`](/documentation/AVFoundation/AVAssetWriterInput/markCurrentPassAsFinished()). You can use the [`respondToEachPassDescription(on:using:)`](/documentation/AVFoundation/AVAssetWriterInput/respondToEachPassDescription(on:using:)) to have the system call you at the beginning of each pass. This property is key-value observable. The system doesn’t notify an observer on a specific thread. --- 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)