FB12196620: It should be possible to modify AVMetadataItem of an AVAsset without having to fully load the video and then export it about reports HOT 2 OPEN

Apple reply:

Is the AVAsset a QuickTime movie file (.mov) or an MPEG file (e.g., .mp4)? These correspond to the UTI types AVFileTypeQuickTimeMovie and AVFileTypeMPEG4.

If so, have you tried:

• open the source file using AVMutableMovie

• update the metadata using its metadata property and replace with the new or updated AVMetadataItem(s)

• rewrite the movie header back to the file using the AVMovie method defined in AVMovie.h:

  • (BOOL)writeMovieHeaderToURL:(NSURL *)URL fileType:(AVFileType)fileType options:(AVMovieWritingOptions)options error:(NSError * _Nullable * _Nullable)outError;

Use the AVMovieWritingAddMovieHeaderToDestination AVMovieWritingOptions value to rewrite the header to the movie file while leaving existing media data in place. You may want to do this in a copy of the source media file.

There’s a WWDC 2015 session video “Editing Movies in AVFoundation” that introduces the API at https://developer.apple.com/wwdc15/506.

If the AVAsset is for other kinds of files than movie files, please let us know the kinds of assets that are important to you for such support.

from reports.

My reply:

Thanks for sharing. That is very useful. My use-case is editing the metadata of audio (M4A) files. I’ll try to see if it works with audio-only files too.

I do think it would be useful to have an easy to use API on AVAsset for this (and for video). For example, await AVAsset.setMetadata([AVMetadataItem], for url: URL).

from reports.