How to loop audio while merging audio and video - ios

Question

I am following this code to merge audio and video files. It works great. Suppose, audio length is 5 seconds and video length is 20 seconds. While I merged this files in the exported video there is no sound after 5 second. That is obvious cause my audio length is 5 seconds. But is it possible to run the audio in loop throughout the full video session.
var finalVideoURL = NSURL()
var finalVideoName = String()
func mergeAudio&VideoFiles(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)
try mutableCompositionAudioTrack[0].insertTimeRange(CMTimeRangeMake(kCMTimeZero, aVideoAssetTrack.timeRange.duration), of: aAudioAssetTrack, at: 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)
finalVideoURL = NSURL(fileURLWithPath: NSHomeDirectory() + "/Documents/FinalVideo.mp4")
finalVideoName = "FinalVideo.mp4"
let assetExport: AVAssetExportSession = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality)!
assetExport.outputFileType = AVFileTypeMPEG4
assetExport.outputURL = finalVideoURL as URL
assetExport.shouldOptimizeForNetworkUse = true
assetExport.exportAsynchronously { () -> Void in
switch assetExport.status {
case AVAssetExportSessionStatus.completed:
print("Export movie to document directory from trimmed audio and mutable video complete :)")
case AVAssetExportSessionStatus.failed:
print("failed \(assetExport.error)")
case AVAssetExportSessionStatus.cancelled:
print("cancelled \(assetExport.error)")
default:
print("complete")
}
}
}

Answer 1

It was asked a long time ago, but it can certainly help someone in the future,
you can do it by inserting the time range of the AVAssetTrack multiple times:
let vDuration = aVideoAsset.duration
let audioAssetTrack = mixComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)
do {
var currentDuration = CMTime.zero
while currentDuration < vDuration {
let restTime = CMTimeSubtract(vDuration, currentDuration)
let maxTime = CMTimeMinimum(aAudioAsset.duration, restTime)
try audioAssetTrack.insertTimeRange(CMTimeRangeMake(start: CMTime.zero, duration: maxTime),
of: aAudioAsset.tracks(withMediaType: .audio)[0],
at: currentDuration)
currentDuration = CMTimeAdd(currentDuration, aAudioAsset.duration)
}
} catch {
print("Failed to load audio track")
continue
}