ios - Weird behaviour of AVMutableComposition freezing while using AVMutableVideoComposition -

i trying merge multiple videos using avmutablecomposition. problem face whenever try add avmutablevideocomposition applying instructions, playback freezes in avplayer @ exact 6 seconds duration.

another interesting thing plays fine if play in photos app of ipad after exporting using same videocomposition. why freezes in avplayer @ 6 seconds?

code:

avmutablecomposition *mutablecomposition = [avmutablecomposition composition];      avmutablecompositiontrack *videocompositiontrack = [mutablecomposition addmutabletrackwithmediatype:avmediatypevideo                                                                                         preferredtrackid:kcmpersistenttrackid_invalid];      avmutablecompositiontrack *audiocompositiontrack = [mutablecomposition addmutabletrackwithmediatype:avmediatypeaudio                                                                                        preferredtrackid:kcmpersistenttrackid_invalid];      (avurlasset *asset in assets)     {             avassettrack *assettrack;             assettrack = [[asset trackswithmediatype:avmediatypevideo] objectatindex:0];             avassettrack *audioassettrack = [asset trackswithmediatype:avmediatypeaudio].firstobject;               nserror *error;             [videocompositiontrack inserttimerange:cmtimerangemake(kcmtimezero, assettrack.timerange.duration )                                                    oftrack:assettrack                                                     attime:time                                                      error:&error];              if (error) {                 nslog(@"asset url :: %@",assettrack.asset);                 nslog(@"error1 - %@", error.debugdescription);             }              [audiocompositiontrack inserttimerange:cmtimerangemake(kcmtimezero, audioassettrack.timerange.duration)                                                oftrack:audioassettrack                                                 attime:time                                                  error:&error];              if (error) {                 nslog(@"error2 - %@", error.debugdescription);             }              time = cmtimeadd(time, assettrack.timerange.duration);              if (cgsizeequaltosize(size, cgsizezero)) {                 size = assettrack.naturalsize;;             }         }          avmutablevideocompositioninstruction *maininstruction = [avmutablevideocompositioninstruction videocompositioninstruction];         avmutablevideocompositionlayerinstruction *videotracklayerinstruction =  [avmutablevideocompositionlayerinstruction videocompositionlayerinstructionwithassettrack:videocompositiontrack];          maininstruction.timerange = cmtimerangemake(kcmtimezero, time);         maininstruction.layerinstructions = [nsarray arraywithobjects:videotracklayerinstruction, nil];         avmutablevideocomposition *maincompositioninst = [avmutablevideocomposition videocomposition];         maincompositioninst.instructions = [nsarray arraywithobject:maininstruction];         maincompositioninst.frameduration = cmtimemake(1, 30);         maincompositioninst.rendersize = size;          pi = [avplayeritem playeritemwithasset:mutablecomposition];         pi.videocomposition = maincompositioninst; 

also, know problem videocomposition because if remove videocomposition, plays fine on avplayer.

update 1: found out when freezes after 6 seconds, if drag slider or forward(i.e. use seektotime), starts playing again without further freeze.

also audio keeps on playing fine when video frozen.

update 2: if go ahead , export using avassetexportsession same avmutablecomposition, , load asset of exported video, works fine. when play avmutablecomposition directly, problem arises.

finally, got solution fix this.

you should play after playeritem's status changed .readytoplay.

please see below.

func startvideoplayer() {     let playeritem = avplayeritem(asset: self.composition!)     playeritem.videocomposition = self.videocomposition!      let player = avplayer(playeritem: playeritem)     player.actionatitemend = .none      videoplayerlayer = avplayerlayer(player: player)     videoplayerlayer!.frame = self.bounds      /* add playeritem's observer */     player.addobserver(self, forkeypath: "player.currentitem.status", options: .new, context: nil)      nsnotificationcenter.defaultcenter().addobserver(self, selector: "playeritemdidreachend:", name: avplayeritemdidplaytoendtimenotification, object: playeritem);      self.layer.addsublayer(videoplayerlayer!) }  override func observevalueforkeypath(keypath: string?, ofobject object: anyobject?, change: [string : anyobject]?, context: unsafemutablepointer<void>) {     if keypath != nil && keypath! == "player.currentitem.status" {         if let newvalue = change?[nskeyvaluechangenewkey] {             if avplayerstatus(rawvalue: newvalue as! int) == .readytoplay {                 playvideo() /* play after status changed .readytoplay */             }         }     } else {         super.observevalueforkeypath(keypath, ofobject: object, change: change, context: context)     } }      func playeritemdidreachend(notification: nsnotification) {     let playeritem = notification.object as! avplayeritem     playeritem.seektotime(kcmtimezero)      playvideo() }   func playvideo() {     videoplayerlayer?.player!.play() }