swift - iOS - change volume for each AVAssetTrack -

i have audio files need insert in avmutablecomposition. each audio have different volume. accomplish created avmutabletrackcomposition , avassettrack each audio file. change volume every track using instance of avmutableaudiomix.

let composition = avmutablecomposition() var trackmixarray = nsmutablearray()  audio in layer{    let trackaudio:avmutablecompositiontrack = composition.addmutabletrackwithmediatype(avmediatypeaudio, preferredtrackid: cmpersistenttrackid())     let file = project.stringbyappendingpathcomponent(audio.name)    let soundasset = avurlasset(url: nsurl(fileurlwithpath: file), options: option [nsobject : anyobject])    let sounds = soundasset.trackswithmediatype(avmediatypeaudio)    var sound:avassettrack = sounds[0] as! avassettrack    let duration:cmtime = sound.timerange.duration     let audiotimerange:cmtimerange = cmtimerangefromtimetotime(kcmtimezero, duration)    let start:cmtime = cmtimemakewithseconds(audio.start.todouble()!, 600)    let stop:cmtime = cmtimemakewithseconds(audio.stop.todouble()!, 600)     let trackmix = avmutableaudiomixinputparameters(track: trackaudio)    trackmix.setvolume(audio.volume, attime: kcmtimezero)    trackmixarray.addobject(trackmix)     trackaudio.inserttimerange(audiotimerange, oftrack: sound, attime: start, error: nil)  }  let audiomix = avmutableaudiomix() audiomix.inputparameters = trackmixarray [anyobject] 

using single avmutablecompositiontrack more avassettrack associated doesn't allow me change volume each track.

 let trackmix = avmutableaudiomixinputparameters(track: sound)  trackmix.setvolume(audio.volume, attime: kcmtimezero)  trackmixarray.addobject(trackmix) 

it's possible change volume directly avassettrack?

    avmutablecomposition *collagecomposition = [[avmutablecomposition alloc]init];         ...         magic         ...     nsarray *trackstoduck = [collagecomposition trackswithmediatype:avmediatypeaudio];             audiomix = [avmutableaudiomix audiomix];             nsmutablearray *trackmixarray = [nsmutablearray array];             (int = 0; < [trackstoduck count]; i++) {                 avmutableaudiomixinputparameters *trackmix = [avmutableaudiomixinputparameters audiomixinputparameterswithtrack:[trackstoduck objectatindex:i]];                         [trackmix setvolume:volume attime:kcmtimezero];                 [trackmixarray addobject:trackmix];             }             audiomix.inputparameters = trackmixarray;      ...      avassetexportsession magic     ...     generalexporter = [[avassetexportsession alloc] initwith...     generalexporter.audiomix = audiomix; 

this should change volume in each track, change swift.

edit: each avmutablecompositiontrack have segments, each segment have starttime , duration, can use avmutableaudiomixinputparameters change volume each cmtimerange

 - (void)setvolumerampfromstartvolume:(float)startvolume                          toendvolume:(float)endvolume                            timerange:(cmtimerange)timerange