OpenTimelineIO-AVFoundation

Realtime playback of OpenTimelineIO files with the sample app OpenTimelineIO Reader:

Note

This library is under heavy development!

General

This Swift Package extends OpenTimelineIO's Swift Bindings to provide functionality for Apple platforms.

The goal is to enable easy interoperability OpenTimelineIO and AVFoundation objects in a correct, lossless and useful manner to enable real world workflows.

• Load OpenTimeline IO files into OTIO Timeline objects and introspect using the standard Swift bindings.
• Create AVFoundation AVComposition AVVideoComposition and AVAudioMix objects from an OTIO Timeline instance allowing for playback via AVPlayer and export via AVExportSession or AVAssetWriter to Quicktime compatible file formats.
• Convert your own edits as AVMutableCompositions into a OTIO Timeline

This library should be compatible with the following Apple platforms:

• macOS
• iOS
• visionOS

but to date has only been extensively tested on macOS

Quickstart for Users

• Download the latest release of the OpenTimelineIO Reader.

• The app should register itself as a reader of OTIO files.

  • In theory should be able to double click a .otio file which will launch the app, or control click with open as.

• To ensure the widest media support possible, please make sure to install Apple's Pro Video Formats package.

  • If you have Final Cut Pro X, Compressor or Motion, this step is unnecessary.
  • Please note that not all video formats are supported, not are image sequences. See Video Format Compatibilty

• Thats it!

Quicktart for Developers:

OpenTimelineIO to AVFoundation:

Assuming you have a basic AVPlayer setup, this will let you import a .otio file with basic jump cut editing. See roadmap for transitions / effects.

    do {
        if
            let timeline = try Timeline.fromJSON(url: url) as? Timeline,
            let (composition, videoComposition, audioMix) = try await timeline.toAVCompositionRenderables()
        {
            let playerItem = AVPlayerItem(asset: composition)
            playerItem.videoComposition = videoComposition
            playerItem.audioMix = audioMix

            self.player.replaceCurrentItem(with: playerItem)
        }
    }
    catch
    {
        print(error)
    }

AVFoundation to OpenTimelineIO:

Assuming you have succssfuly created an AVCompostion - this will export a basic .otio file without effects or transition metadata. See roadmap for transitions / effects.

    do {
        let timeline = try compositon.toOTIOTimeline(named: toURL.lastPathComponent)
        try timeline.toJSON(url: toURL)
    }
    catch
    {
        print(error)
    }

OpenTimelineIO Extensions

• Conversion of OpenTimelineIO RationalTime to CoreMedia CMTime
• Conversion of OpenTimelineIO TimeRange to CoreMedia CMTimeRange
• Conversion of OpenTimelineIO ExternalReference to AVFoundation AVAsset
• Conversion of OpenTimelineIO Timeline to playable/exportable AVFoundation AVCompostion AVVideoCompostion and AVAudioMix

Core Media Extensions

• Conversion of CoreMedia CMTime to OpenTimelineIO RationalTime
• Conversion of CoreMedia CMTimeRange to OpenTimelineIO TimeRange

AVFoundation Extensions

• Conversion of AVCompositionTrackSegment to OpenTimelineIO Clip with an embedded OpenTimelineIO ExternalReference which has url metadata
• Conversion of AVCompositionTrack to OpenTimelineIO Track with each AVCompositionTrackSegment converted to OpenTimelineIO Clip associations
• Conversion of AVComposition to OpenTimelineIO Timeline with associated Tracks converted

Compatibility:

OTIO Format Compatibility Matrix

NLE Compatibility

Project Validation

Video Format Compatibility

Generally if Quicktime or Final Cut Pro X Can support it, it should just work.

Dependencies

• OpenTimelineIO's Swift Bindings for Swift interoperabiloty
• TimecodeKit for reading and parsing Time Code from AVAsset's

Roadmap

• Enable viable metadata from AVAssets to ExternalRefernce and other objects where appropriate to faciliate correctness and robustness in conversion.

  • Waiting on #51

• Enable robust support for transitions / effects metadata to be passed between AVFoundation and OTIO

  • This requires thinking deeply how to support transitions and effects, and the infrasturcture required (custom instructions, composition renderers, etc).
  • Input welcome!

FAQ

• Why does RationalTime seconds, rate and value differ from a converted CMTIme?

RationalTime uses double as numerator and denimonator for rational time calculations. CMTime uses Int64 and Int32 for its value and time base. In order to get most accurate conversions, OpenTimleineIO-AVFoundation uses looks at the number of decimal places in a RationalTime representation and scales it to a whole number to maximally represent the same ratio without rounding or truncating which would happen with naive Double <-> Int casting.

See our Unit tests for conversion notes. In general, for integer frame rates (ie 120, 60, 30, 25, 24) there is zero loss conversions. For non integer frame rates like 59.97, 29.97, 24.98 (23.976) there may be very minor differences in the conversions as of today (our Unit testing uses an accuracy factor of 0.00000000001 )

If you have ideas on lossless conversion, PR's are welcome! This was a first pass :)

Credits:

OpenTimelineIO and TimecodeKit, and Ozu.ai for supporting this effort.