Swift: Accessing metadata from AVAsset

Most assets like movies, music and TV shows from the iTunes Store come with a lot of metadata like artwork, release date, length etc. Or if you’re like me and add this data to your own files with a tool like Subler. With the help of AVFoundation you are able to access this data in your iOS and macOS apps, but it’s not as straight forward and the documentation very sparse, which is why this post will help you master all this.

Prerequisites

• Have a media file with metadata in your project
• import AVFoundation
• Create an AVAsset from your file

1.

Fetch the metadata from your asset like this:

let metadata = asset.metadata(forFormat: AVMetadataFormatiTunesMetadata)

2.

Access the desired field with keySpace and key I’ve noticed that Apple does not have much documentation on the keys they use and these might change, but here is a list:

keySpace: ‘itsk’

• Name: ‘©nam’
• Artwork: ‘covr’
• Artist: ‘©ART’
• Writer: ‘©wrt’
• Description: ‘desc’
• Long Description: ‘ldes’
• Genres: ‘©gen’
• Release date: ‘©day’
• Executive Producers: ‘©xpd’
• HD: ‘hdvd’
  • 0: No
  • 1: 720p
  • 2: 1080p
• Media type: ‘stik’
  • 9: Movie

keySpace: ‘itlk’

• Age rating: ‘com.apple.iTunes.iTunEXTC’
• Cast, Directors, Screenwriters, and Studio (.plist): ‘com.apple.iTunes.iTunMOVI’

3.

Extract the metadata field you like: Note: Most of these are stored as strings

let titleItems = AVMetadataItem.metadataItems(from: metadata, withKey: "©nam", keySpace: "itsk")
if let data = titleItems.first, let title = data.stringValue {
    print(title)
}

3.1

The iTunMOVI field is a little harder, as it is a .plist which you first have to serialize. Here is an example of how to obtain these fields:

let extendedInfo = AVMetadataItem.metadataItems(from: metadata, withKey: "com.apple.iTunes.iTunMOVI", keySpace: "itlk")
if let first = extendedInfo.first {
    do {
        let plistData = try PropertyListSerialization.propertyList(
            from: first.stringValue?.data(using: .utf8) ?? Data(), 
            options: .mutableContainersAndLeaves, format: nil
        ) as! [String:AnyObject]

        print(plistData["cast"].map({$0.value(forKey: "name")}) as? [String] ?? [])
        print(plistData["directors"].map({$0.value(forKey: "name")}) as? [String] ?? [])
        print(plistData["screenwriters"].map({$0.value(forKey: "name")}) as? [String] ?? [])

    } catch {
        print("Error reading plist: \(error.localizedDescription)")
    }
}

Summary

I’m glad Apple offers a way to access this data on iOS, even though it is not quite intuitive. I hope this little guide helped you to get around some of the obstacles.