Error NSLocalizedDescription=Cannot Save

Question

I was trying to merge audio and Video. I was following this link. I am getting a error but I don't understand what's wrong.

failed Optional(Error Domain=AVFoundationErrorDomain Code=-11823 "Cannot Save" UserInfo={NSLocalizedDescription=Cannot Save, NSLocalizedRecoverySuggestion=Try saving again.})

This my code:

import UIKit
import AVFoundation
import AVKit
import AssetsLibrary

class ViewController: UIViewController {
    func mergeFilesWithUrl(videoUrl:NSURL, audioUrl:NSURL)
    {
        let mixComposition : AVMutableComposition = AVMutableComposition()
        var mutableCompositionVideoTrack : [AVMutableCompositionTrack] = []
        var mutableCompositionAudioTrack : [AVMutableCompositionTrack] = []
        let totalVideoCompositionInstruction : AVMutableVideoCompositionInstruction = AVMutableVideoCompositionInstruction()

        //start merge
        let aVideoAsset : AVAsset = AVAsset(url: videoUrl as URL)
        let aAudioAsset : AVAsset = AVAsset(url: audioUrl as URL)

        mutableCompositionVideoTrack.append(mixComposition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid))
        mutableCompositionAudioTrack.append( mixComposition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid))

        let aVideoAssetTrack : AVAssetTrack = aVideoAsset.tracks(withMediaType: AVMediaTypeVideo)[0]
        let aAudioAssetTrack : AVAssetTrack = aAudioAsset.tracks(withMediaType: AVMediaTypeAudio)[0]

        do{
            try mutableCompositionVideoTrack[0].insertTimeRange(CMTimeRangeMake(kCMTimeZero, aVideoAssetTrack.timeRange.duration), of: aVideoAssetTrack, at: kCMTimeZero)

            //In my case my audio file is longer then video file so i took videoAsset duration
            //instead of audioAsset duration

            try mutableCompositionAudioTrack[0].insertTimeRange(CMTimeRangeMake(kCMTimeZero, aVideoAssetTrack.timeRange.duration), of: aAudioAssetTrack, at: kCMTimeZero)

            //Use this instead above line if your audiofile and video file's playing durations are same

            //            try mutableCompositionAudioTrack[0].insertTimeRange(CMTimeRangeMake(kCMTimeZero, aVideoAssetTrack.timeRange.duration), ofTrack: aAudioAssetTrack, atTime: kCMTimeZero)
        }catch{
        }

        totalVideoCompositionInstruction.timeRange = CMTimeRangeMake(kCMTimeZero,aVideoAssetTrack.timeRange.duration )

        let mutableVideoComposition : AVMutableVideoComposition = AVMutableVideoComposition()
        mutableVideoComposition.frameDuration = CMTimeMake(1, 30)
        mutableVideoComposition.renderSize = CGSize(width: 1280, height: 720)

        //find your video on this URl
        let savePathUrl : NSURL = NSURL(fileURLWithPath: NSHomeDirectory() + "/Documents/newVideo.mp4")

        let assetExport: AVAssetExportSession = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality)!
        assetExport.outputFileType = AVFileTypeMPEG4
        assetExport.outputURL = savePathUrl as URL
        assetExport.shouldOptimizeForNetworkUse = true

        assetExport.exportAsynchronously { () -> Void in
            switch assetExport.status {

            case AVAssetExportSessionStatus.completed:
                //Uncomment this if u want to store your video in asset
                //let assetsLib = ALAssetsLibrary()
                //assetsLib.writeVideoAtPathToSavedPhotosAlbum(savePathUrl, completionBlock: nil)

                print("success")
            case  AVAssetExportSessionStatus.failed:
                print("failed \(String(describing: assetExport.error))")
            case AVAssetExportSessionStatus.cancelled:
                print("cancelled \(String(describing: assetExport.error))")
            default:
                print("complete")
            }
        }
    }

    @IBAction func marge(_ sender: Any) {
        let videoUrl : NSURL =  NSURL(fileURLWithPath: Bundle.main.path(forResource: "desp", ofType: "mp4")!)
        let audioUrl : NSURL = NSURL(fileURLWithPath: Bundle.main.path(forResource: "Desp", ofType: "mp3")!)

        mergeFilesWithUrl(videoUrl: videoUrl, audioUrl: audioUrl)
    }
}

Answer 1

I ran into this problem, too. Try to add these couple lines of code and it shall solve the problem.

do { // delete old video
        try FileManager.default.removeItem(at: savePathUrl)
    } catch { print(error.localizedDescription) }

It will delete the old file in this directory.