# replacementEmbeddedThumbnailPixelBuffer(withPhotoFormat:for:) A callback in which you can provide a replacement embedded thumbnail image with compression settings, or strip the existing embedded thumbnail image from the flattened file. ``` optional func replacementEmbeddedThumbnailPixelBuffer(withPhotoFormat replacementEmbeddedThumbnailPhotoFormatOut: AutoreleasingUnsafeMutablePointer, for photo: AVCapturePhoto) -> Unmanaged? ``` ## Parameters `replacementEmbeddedThumbnailPhotoFormatOut` A pointer to a dictionary of keys and values from `AVFoundation/AVVideoSettings.h`. If you pass a non-nil dictionary, [`AVVideoCodecKey`](/documentation/AVFoundation/AVVideoCodecKey) is required, with `width` and `height` keys optional. `photo` The calling instance of [`AVCapturePhoto`](/documentation/AVFoundation/AVCapturePhoto) whose file metadata you’re modifying. ## Return Value A pixel buffer containing a source image to be encoded to the file as the replacement thumbnail image. To preserve the existing embedded thumbnail photo to the flattened data, set `replacementEmbeddedThumbnailPhotoFormatOut` to `photo.embeddedThumbnailPhotoFormat` and return `nil`. To replace the existing embedded thumbnail, pass a replacement photo format dictionary and return a non-`nil` replacement pixel buffer. To remove the existing embedded thumbnail, set `replacementEmbeddedThumbnailPhotoFormatOut` to `nil` and return `nil`. ## Discussion This callback is optional. If your delegate doesn’t implement this callback, the existing metadata in the in-memory [`AVCapturePhoto`](/documentation/AVFoundation/AVCapturePhoto) container is written directly to the file data representation. --- 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)