ScaleVideo.swift

Uniformly scales video in time domain

Learn more about scaling video files from our in-depth blog post.

The associated Xcode project implements a SwiftUI app for macOS and iOS that scales video files stored on your device or iCloud.

A default video file is provided to set the initial state of the app.

After a video is imported it is displayed in the VideoPlayer where it can be viewed, along with its scaled counterpart.

Select the scale factor from a slider.

Classes

The project is comprised of:

1. ScaleVideoApp - The App for import, scale and export.
2. ScaleVideoObservable - An ObservableObject that manages the user interaction to scale and play video files.
3. ScaleVideo - The AVFoundation and vDSP code that reads, scales and writes video files.

ScaleVideoApp

Videos to scale are imported from Files using fileImporter and exported to Files using fileExporter.

The scaling is monitored with a ProgressView.

The video and scaled video can be played with a VideoPlayer.

ScaleVideoObservable

Creates the ScaleAudio object to perform the scaling operation and send progress back to the app.

The URL of the video to scale is received from the file import operation and, if needed, downloaded with startDownloadingUbiquitousItem or security accessed with startAccessingSecurityScopedResource.

To facilitate exporting using fileExporter a FileDocument named VideoDocument is prepared with a FileWrapper created from the URL of the scaled video.

ScaleVideo

Scaling video is performed using AVFoundation and vDSP.

The ScaleVideo initializer init:

init?(path : String, desiredDuration: Float64, frameRate: Int32, destination: String, progress: @escaping (CGFloat, CIImage?) -> Void, completion: @escaping (URL?, String?) -> Void)

Arguments:

1. path: String - The path of the video file to be scaled.

2. desiredDuration: Float64 - The desired duration in seconds of the scaled video.

3. frameRate: Int32 - The desired frame rate of the scaled video.

4. destination: String - The path of the scaled video file.

5. progress: Closure - A handler that is periodically executed to send progress images and values.

6. completion: Closure - A handler that is executed when the operation has completed to send a message of success or not.

Example usage is provided in the code:

func testScaleVideo() {
    let fm = FileManager.default
    let docsurl = try! fm.url(for:.documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
    
    let destinationPath = docsurl.appendingPathComponent("DefaultVideoScaled.mov").path
    let scaleVideo = ScaleVideo(path: kDefaultURL.path, desiredDuration: 8, frameRate: 30, expedited: false, destination: destinationPath) { p, _ in
        print("p = \(p)")
    } completion: { result, error in
        print("result = \(String(describing: result))")
    }
    
    scaleVideo?.start()
}