Play video backwards - ios

Question

What I want is basically reverse an AVAsset and output video file and I found this link -
https://github.com/tempire/ReverseAVAsset/blob/master/AVAsset.swift
This is what I did:
import UIKit
import AVFoundation
import AVKit
class ViewController: UIViewController {
var playerViewController = AVPlayerViewController()
var playerView = AVPlayer()
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let path = Bundle.main.path(forResource: "video", ofType: "mov")
let outputUrl = URL(fileURLWithPath: "\(NSUUID().uuidString)video.mov")
let originalAsset = AVAsset(url: URL(fileURLWithPath: path!))
let reversedAsset = originalAsset.reversedAsset(outputUrl)
playerView = AVPlayer(playerItem: AVPlayerItem(asset: reversedAsset!))
playerViewController.player = playerView
present(playerViewController, animated: true) {
self.playerViewController.player?.play()
}
}
}
But its not working and this is what I end up with:
I think I'm doing something wrong with outputURL, please help if you know what to do

Answer 1

Problem was with output URL, this is the correct way to do
import UIKit
import AVFoundation
import AVKit
class ViewController: UIViewController {
var playerViewController = AVPlayerViewController()
var playerView = AVPlayer()
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let path = Bundle.main.path(forResource: "video", ofType: "mov")
//Correct way
var outputURL: URL?
do {
let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
outputURL = documentsURL.appendingPathComponent("\(NSUUID().uuidString)newvideo.mp4")
}
let originalAsset = AVAsset(url: URL(fileURLWithPath: path!))
let reversedAsset = originalAsset.reversedAsset(outputUrl)
playerView = AVPlayer(playerItem: AVPlayerItem(asset: reversedAsset!))
playerViewController.player = playerView
present(playerViewController, animated: true) {
self.playerViewController.player?.play()
}
}
}

Answer 2

The main issue was there in Method: reversedAsset(outputUrl)
There we try to write the file with a completion handler, and meanwhile we try to play the asset returned by the same method which is not even completely written on disc.
In order to resolve the issue, You've to wait for the method reversedAsset(outputUrl) to finish writing the file.