Composing Video and Audio - Video's audio is gone - swift

Question

My question is, I am using the function below, to compose a video and audio. I want to keep video's original sound but it goes away somehow, I do not have any clue.
I got this function from this answer
I tried to change volumes right after appending AVMutableCompositionTracks but it did not work
For instance;
mutableVideoCompositionTrack.prefferedVolume = 1.0
mutableAudioCompositionTrack.prefferedVolume = 0.05
But still, all you can hear is only the audio file.
The function;
private func mergeAudioAndVideo(audioUrl: URL, videoUrl: URL, completion: #escaping (Bool)->Void){
let mixComposition = AVMutableComposition()
var mutableCompositionVideoTrack : [AVMutableCompositionTrack] = []
var mutableCompositionAudioTrack : [AVMutableCompositionTrack] = []
let totalVideoCompositionInstruction = AVMutableVideoCompositionInstruction()
let videoAsset = AVAsset(url: videoUrl)
let audioAsset = AVAsset(url: audioUrl)
mutableCompositionVideoTrack.append(mixComposition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid))
mutableCompositionAudioTrack.append(mixComposition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid))
mutableCompositionAudioTrack[0].preferredVolume = 0.05
mutableCompositionVideoTrack[0].preferredVolume = 1.0
let videoAssetTrack = videoAsset.tracks(withMediaType: AVMediaTypeVideo)[0]
let audioAssetTrack = audioAsset.tracks(withMediaType: AVMediaTypeAudio)[0]
do {
try mutableCompositionVideoTrack[0].insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAssetTrack.timeRange.duration), of: videoAssetTrack, at: kCMTimeZero)
try mutableCompositionAudioTrack[0].insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAssetTrack.timeRange.duration), of: audioAssetTrack, at: kCMTimeZero)
}catch{
print("ERROR#1")
}
totalVideoCompositionInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, videoAssetTrack.timeRange.duration)
let mutableVideoComposition = AVMutableVideoComposition()
mutableVideoComposition.frameDuration = CMTimeMake(1, 30)
mutableVideoComposition.renderSize = CGSize(width: 1280, height: 720)
//exporting
savePathUrl = try! FileManager.default.url(for: FileManager.SearchPathDirectory.documentDirectory, in: FileManager.SearchPathDomainMask.userDomainMask, appropriateFor: nil, create: true).appendingPathComponent("merged").appendingPathExtension("mov")
let assetExport = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality)!
assetExport.outputFileType = AVFileTypeMPEG4
assetExport.outputURL = savePathUrl
assetExport.shouldOptimizeForNetworkUse = true
do {
try FileManager.default.removeItem(at: savePathUrl)
}catch {
print(error)
}
assetExport.exportAsynchronously {
switch assetExport.status{
case .completed:
print("completed")
completion(true)
default:
print("failed \(assetExport.error!)")
completion(false)
}
}
}

Answer 1

You can adjust volume for video and audio separately #Faruk, Here a is little bit code for that.
//Extract audio from the video and the music
let audioMix: AVMutableAudioMix = AVMutableAudioMix()
var audioMixParam: [AVMutableAudioMixInputParameters] = []
let assetVideoTrack: AVAssetTrack = assetVideo.tracksWithMediaType(AVMediaTypeAudio)[0]
let assetMusicTrack: AVAssetTrack = assetMusic.tracksWithMediaType(AVMediaTypeAudio)[0]
let videoParam: AVMutableAudioMixInputParameters = AVMutableAudioMixInputParameters(track: assetVideoTrack)
videoParam.trackID = compositionAudioVideo.trackID
let musicParam: AVMutableAudioMixInputParameters = AVMutableAudioMixInputParameters(track: assetMusicTrack)
musicParam.trackID = compositionAudioMusic.trackID
//Set final volume of the audio record and the music
videoParam.setVolume(volumeVideo, atTime: kCMTimeZero)
musicParam.setVolume(volumeAudio, atTime: kCMTimeZero)
//Add setting
audioMixParam.append(musicParam)
audioMixParam.append(videoParam)
//Add audio on final record
//First: the audio of the record and Second: the music
do {
try compositionAudioVideo.insertTimeRange(CMTimeRangeMake(kCMTimeZero, assetVideo.duration), ofTrack: assetVideoTrack, atTime: kCMTimeZero)
} catch _ {
assertionFailure()
}
do {
try compositionAudioMusic.insertTimeRange(CMTimeRangeMake(CMTimeMake(Int64(startAudioTime * 10000), 10000), assetVideo.duration), ofTrack: assetMusicTrack, atTime: kCMTimeZero)
} catch _ {
assertionFailure()
}
//Add parameter
audioMix.inputParameters = audioMixParam
let completeMovie = "\(docsDir)/\(randomString(5)).mp4"
let completeMovieUrl = NSURL(fileURLWithPath: completeMovie)
let exporter: AVAssetExportSession = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetHighestQuality)!
exporter.outputURL = completeMovieUrl
exporter.outputFileType = AVFileTypeMPEG4
exporter.audioMix = audioMix
exporter.exportAsynchronouslyWithCompletionHandler({
switch exporter.status {
case AVAssetExportSessionStatus.Completed:
print("success with output url \(completeMovieUrl)")
case AVAssetExportSessionStatus.Failed:
print("failed \(String(exporter.error))")
case AVAssetExportSessionStatus.Cancelled:
print("cancelled \(String(exporter.error))")
default:
print("complete")
}
})
}

Answer 2

Here's the combined code of all the answers. It took me a while to decode those answers so I decided to add it here for any future users:
Swift 5:
enum MixError: Error {
case TimeRangeFailure
case ExportFailure
}
var selectedVideoLevel = 1.0
var selectedMusicLevel = 1.0
func mix(videoUrl: URL, musicUrl: URL, completion: ((Result<URL, Error>) -> Void)?) {
let videoAsset = AVAsset(url: videoUrl)
let musicAsset = AVAsset(url: musicUrl)
let audioVideoComposition = AVMutableComposition()
let audioMix = AVMutableAudioMix()
var mixParameters = [AVMutableAudioMixInputParameters]()
let videoCompositionTrack = audioVideoComposition
.addMutableTrack(withMediaType: .video, preferredTrackID: .init())!
let audioCompositionTrack = audioVideoComposition
.addMutableTrack(withMediaType: .audio, preferredTrackID: .init())!
let musicCompositionTrack = audioVideoComposition
.addMutableTrack(withMediaType: .audio, preferredTrackID: .init())!
let videoAssetTrack = videoAsset.tracks(withMediaType: .video)[0]
let audioAssetTrack = videoAsset.tracks(withMediaType: .audio).first
let musicAssetTrack = musicAsset.tracks(withMediaType: .audio)[0]
let audioParameters = AVMutableAudioMixInputParameters(track: audioAssetTrack)
audioParameters.trackID = audioCompositionTrack.trackID
let musicParameters = AVMutableAudioMixInputParameters(track: musicAssetTrack)
musicParameters.trackID = musicCompositionTrack.trackID
audioParameters.setVolume(selectedVideoLevel, at: .zero)
musicParameters.setVolume(selectedMusicLevel, at: .zero)
mixParameters.append(audioParameters)
mixParameters.append(musicParameters)
audioMix.inputParameters = mixParameters
/// prevents video from unnecessary rotations
videoCompositionTrack.preferredTransform = videoAssetTrack.preferredTransform
do {
let timeRange = CMTimeRange(start: .zero, duration: videoAsset.duration)
try videoCompositionTrack.insertTimeRange(timeRange, of: videoAssetTrack, at: .zero)
if let audioAssetTrack = audioAssetTrack {
try audioCompositionTrack.insertTimeRange(timeRange, of: audioAssetTrack, at: .zero)
}
try musicCompositionTrack.insertTimeRange(timeRange, of: musicAssetTrack, at: .zero)
} catch {
completion?(.failure(MixError.TimeRangeFailure)
}
let exportUrl = FileManager.default
.urls(for: .applicationSupportDirectory, in: .userDomainMask).first?
.appendingPathComponent("\(Date().timeIntervalSince1970)-video.mp4")
let exportSession = AVAssetExportSession(
asset: audioVideoComposition,
presetName: AVAssetExportPresetHighestQuality
)
exportSession?.audioMix = audioMix
exportSession?.outputFileType = .m4v
exportSession?.outputURL = exportUrl
exportSession?.exportAsynchronously(completionHandler: {
guard let status = exportSession?.status else { return }
switch status {
case .completed:
completion?(.success(exportUrl!))
case .failed:
completion?(.failure(MixError.ExportError)
default:
print(status)
}
})
}

Answer 3

I figured it out. It seems an AVAsset which loads a video holds the audio and video separately. So you can reach them writing``
videoAsset.tracks(withMediaType: AVMediaTypeAudio)[0] //audio of a video
videoAsset.tracks(withMediaType: AVMediaTypeVideo)[0] //video of a video(without sound)
So I added these lines to the code and it worked!
var mutableCompositionBackTrack : [AVMutableCompositionTrack] = []
mutableCompositionBackTrack.append(mixComposition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid))
try mutableCompositionBackTrack[0].insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAssetTrack.timeRange.duration), of: backAssetTrack, at: kCMTimeZero)
There is a still missing point that I do not know how to do, and that is setting volumes of these audio assets. I will update this answer as soon as I figure out how.