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VESDK/iOS/Guides/Audio Overlays/Add Overlays

From Remote URL

VideoEditor SDK supports loading audio files from a remote URL, this can be a resource hosted by a hosting provider or your own servers.

For each audio clip, we construct a remote URL from the clip identifier and create a download task. Upon successful download, we save it to a temporary location after checking if a file already exists at that location and removing it if necessary.

In order to keep the UI responsive and prevent race conditions while the audio files are downloading, we dispatch to the main queue. Here, we keep track of the finished download task and the locations of the downloaded clip by writing to a downloadLocations dictionary.

Now once all clips have finished downloading, we can retrieve their local URLs and identifiers from the downloadLocations dictionary and pass them to the AudioClip constructor. AudioClip objects, additionally, hold metadata such as a thumbnailURL and the duration of the clip.

We then need to add the audio clips to an AudioClipCategory object which holds the metadata of the category such as a preview image and a title.

Finally, we can configure the assetCatalog by assigning an array of the audio clip categories we want to include to the audioClips property.

import UIKit
import VideoEditorSDK
class AddAudioOverlaysFromRemoteURLSwift: Example, VideoEditViewControllerDelegate {
// The local locations of the downloaded remote resources.
private var downloadLocations = [String: URL]()
// Although the editor supports adding assets with remote URLs, we highly recommend
// that you manage the download of remote resources yourself, since this
// gives you more control over the whole process. After successfully downloading
// the files you should pass the local URLs to the asset catalog of the configuration.
override func invokeExample() {
// Create a `Video` from a URL to a video in the app bundle.
let video = Video(url: Bundle.main.url(forResource: "Skater", withExtension: "mp4")!)
// Identifiers of remote audio clips.
let elsewhereAudioClipIdentifiers = [
let otherAudioClipIdentifiers = [
// All available identifiers of the audio clips.
let audioClipIdentifiers = elsewhereAudioClipIdentifiers + otherAudioClipIdentifiers
// Download each of the remote resources.
audioClipIdentifiers.forEach { identifier in
guard let remoteURL = URL(string: "\(identifier).mp3") else {
fatalError("Unable to parse URL.")
let downloadTask = URLSession.shared.downloadTask(with: remoteURL) { downloadURL, _, error in
if let error = error {
fatalError("There was an error downloading the file: \(error)")
guard let downloadURL = downloadURL else {
// File was downloaded successfully. Saving it in the temporary directory.
let temporaryDirectoryURL = FileManager.default.temporaryDirectory
let localURL = temporaryDirectoryURL.appendingPathComponent("\(identifier).mp3")
if FileManager.default.fileExists(atPath: localURL.path) {
// Remove the file at the destination if it already exists
try? FileManager.default.removeItem(at: localURL)
try? FileManager.default.moveItem(at: downloadURL, to: localURL)
// Dispatch to the main queue for any UI work
// and to prevent race conditions.
DispatchQueue.main.async {
self.downloadLocations[identifier] = localURL
// If all resources have been downloaded the editor can be started.
if self.downloadLocations.count == audioClipIdentifiers.count {
// Create new audio clip categories with custom audio clips from
// the downloaded resources.
let elsewhereClipsLocations = self.downloadLocations.filter { elsewhereAudioClipIdentifiers.contains($0.key) }
let otherClipsLocations = self.downloadLocations.filter { otherAudioClipIdentifiers.contains($0.key) }
let elsewhereClips = { AudioClip(identifier: $0.key, audioURL: $0.value) }
let otherClips = { AudioClip(identifier: $0.key, audioURL: $0.value) }
let elsewhereAudioClipCategory = AudioClipCategory(title: "Elsewhere", imageURL: nil, audioClips: elsewhereClips)
let otherAudioClipCategory = AudioClipCategory(title: "Other", imageURL: nil, audioClips: otherClips)
// Create a `Configuration` object.
let configuration = Configuration { builder in
// Add the custom audio clips to the asset catalog.
builder.assetCatalog.audioClips = [elsewhereAudioClipCategory, otherAudioClipCategory]
// Create the video editor. Make this class the delegate of it to handle export and cancelation.
let videoEditViewController = VideoEditViewController(videoAsset: video, configuration: configuration)
videoEditViewController.delegate = self
// Reenable user interaction. In production you would want to dismiss a progress indicator for example.
self.presentingViewController?.view.isUserInteractionEnabled = true
// Present the video editor.
videoEditViewController.modalPresentationStyle = .fullScreen
self.presentingViewController?.present(videoEditViewController, animated: true, completion: nil)
// Disable user interaction while the download is active. In production you would want to show a progress indicator for example.
self.presentingViewController?.view.isUserInteractionEnabled = false
// Start the file download
// Removes the previously downloaded resources.
private func removeResources() {
for location in downloadLocations.values {
try? FileManager.default.removeItem(at: location)
// MARK: - VideoEditViewControllerDelegate
func videoEditViewControllerShouldStart(_ videoEditViewController: VideoEditViewController, task: VideoEditorTask) -> Bool {
// Implementing this method is optional. You can perform additional validation and interrupt the process by returning `false`.
func videoEditViewControllerDidFinish(_ videoEditViewController: VideoEditViewController, result: VideoEditorResult) {
// The user exported a new video successfully and the newly generated video is located at `result.output.url`. Dismissing the editor.
presentingViewController?.dismiss(animated: true, completion: {
func videoEditViewControllerDidFail(_ videoEditViewController: VideoEditViewController, error: VideoEditorError) {
// There was an error generating the video.
// Dismissing the editor.
presentingViewController?.dismiss(animated: true, completion: {
func videoEditViewControllerDidCancel(_ videoEditViewController: VideoEditViewController) {
// The user tapped on the cancel button within the editor. Dismissing the editor.
presentingViewController?.dismiss(animated: true, completion: {