Silence is not adding on end of an audio file

Question

I'm working on a demo of how to add extra silence audio at the end of a given audio file.

here my audio file length is 29 sec. & I'm adding 11-sec silence. so, final output audio length will be 40 sec.

Here is my function,

func addSilenceInAudio(inputFilePath:URL, silenceTime: Int, minimumAudioLength: Int, completionBlock:@escaping ((String?, Error?) -> Void)) {

        let asset = AVURLAsset(url: inputFilePath, options: nil)

        //get an original audio length

        let endAudioTime = CMTimeMake(value: Int64(silenceTime), timescale: 1)

        let composition = AVMutableComposition()

        let insertAt = CMTimeRange(start: CMTime.zero , end: endAudioTime)
        let assetTimeRange = CMTimeRange(start: CMTime.zero, end:asset.duration)

        //here i'm inserting range
        try! composition.insertTimeRange(assetTimeRange, of: asset, at: insertAt.end)

        let exportSessionNew = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetAppleM4A)
        exportSessionNew?.outputFileType = AVFileType.m4a
        let documentURL = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
        let dateString = (Date().millisecondsSince1970) //added file name here
        let outputURL = documentURL.appendingPathComponent("\(dateString).m4a") //file name must be .m4a
        exportSessionNew?.outputURL = outputURL //output url

        exportSessionNew?.exportAsynchronously(completionHandler: {
            () -> Void in
            print(exportSessionNew as Any)
            if exportSessionNew!.status == AVAssetExportSession.Status.completed  {
                // All is working fine!!
                print(exportSessionNew?.outputURL as Any) //get outputfile
                print("success")
                completionBlock("\(String(describing: exportSessionNew?.outputURL))", nil)
            } else {
                print("failed")
                completionBlock(nil, exportSessionNew?.error)
            }
        })
    }

above code is working fine & I'm getting my output audio with 40 sec.

but the Problem is 11-sec silence is adding in starting of an audio file.

it should be at the end of an audio file.

I'm doing something wrong here?

Answer 1

You basically only need to extend the length of the audio.

So...

let assetTimeRange = CMTimeRange(start: CMTime.zero, end:asset.duration)

change to something like

let newDuration = asset.duration + silenceTime
let assetTimeRange = CMTimeRange(start: CMTime.zero, end:newDuration)

Disclaimer: It's a while since I've done this