AVPlayer.play() in UITableViewCell briefly blocks UI

Question

I’m trying add inline videos to my UITableViewCells a la Instagram, Twitter, Vine…etc. I’m testing out the UI with a local video file using AVPlayerController and a custom cell (see sample code below). I wait for the status of the AVPlayer to be ReadyToPlay and then play the video.

The issue is that when scrolling on the tableView the UI freezes for a fraction of section whenever a video cell is loaded which makes the app seem clunky. This effect is made worse when there are multiple video cells in a row. Any thoughts and help would be greatly appreciated

TableView Code:

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

     let cell = tableView.dequeueReusableCellWithIdentifier("videoCell", forIndexPath: indexPath) as! CustomCell

     //Set up video player if cell doesn't already have one
     if(cell.videoPlayerController == nil){
         cell.videoPlayerController = AVPlayerViewController()
         cell.videoPlayerController.view.frame.size.width = cell.mediaView.frame.width
         cell.videoPlayerController.view.frame.size.height = cell.mediaView.frame.height 
         cell.videoPlayerController.view.center = cell.mediaView.center
         cell.mediaView.addSubview(cell.videoPlayerController.view) 
     }

     //Remove old observers on cell.videoPlayer if they exist
     if(cell.videoObserverSet){
         cell.videoPlayer.removeObserver(cell, forKeyPath: "status")
     }


     let localVideoUrl: NSURL = NSBundle.mainBundle().URLForResource("videoTest", withExtension: "m4v")!
     cell.videoPlayer = AVPlayer(URL:localVideoUrl)
     cell.videoPlayer.addObserver(cell, forKeyPath:"status", options:NSKeyValueObservingOptions.New, context = nil)
     cell.videoObserverSet = true         

     cell.videoPlayerController.player = cell.videoPlayer


     return cell
}

Custom Cell Observer Code:

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {

    if(keyPath=="status"){
        print("status changed on cell video!");

        if(self.videoPlayer.status == AVPlayerStatus.ReadyToPlay){

            dispatch_async(dispatch_get_main_queue(), { () -> Void in
                self.videoPlayer.play()
            })
        }
    }
}

I also tried loading an AVAsset version of the video using the loadValuesAsynchronouslyForKeys(["playable"]) but that didn't help with the UI block either.

What can I do to get the silky smooth video playback and scrolling of Instagram?

Answer 1

Another Update Highly recommend using Facebook's Async Display Kit ASVideoNode as a drop in replacement for AVPlayer. You'll get the silky smooth Instagram tableview performance while loading and playing videos. I think AVPlayer runs a few processes on the main thread and there's no way to get around them cause it's happening at a relatively low level.

Update: Solved

I wasn't able to directly tackle the issue, but I used to some tricks and assumptions and to get the performance I wanted.

The assumption was that there's no way to avoid the video taking a certain amount of time to load on the main thread (unless you're instagram and you possess some AsyncDisplayKit magic, but I didn't want to make that jump), so instead of trying to remove the UI block, try to hide it instead.

I hid the UIBlock by implementing a simple isScrolling check on on my tableView

func scrollViewDidEndDragging(scrollView: UIScrollView, willDecelerate decelerate: Bool) {

    if(self.isScrolling){
        if(!decelerate){
            self.isScrolling = false
            self.tableView.reloadData()
        }
    }
}

func scrollViewDidEndDecelerating(scrollView: UIScrollView) {

    if(self.isScrolling){
        self.isScrolling = false
        self.tableView.reloadData()
    }
}

func scrollViewWillBeginDragging(scrollView: UIScrollView) {
    self.isScrolling = true
}

And then just made sure not to load the video cells when tableView is scrolling or a video is already playing, and reload the the tableView when the scrolling stops.

if(!isScrolling && cell.videoPlayer == nil){

    //Load video cell here
}

But make sure to remove the videoPlayer, and stop listening to replay notifications once the videoCell is not on the screen anymore.

func tableView(tableView: UITableView, didEndDisplayingCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {

    if(tableView.indexPathsForVisibleRows?.indexOf(indexPath) == nil){

        if (cell.videoPlayer != nil && murmur.video_url != nil){

            if(cell.videoPlayer.rate != 0){

                cell.videoPlayer.removeObserver(cell, forKeyPath: "status")
                cell.videoPlayer = nil;
                cell.videoPlayerController.view.alpha = 0;
            }
        }
    }
}

With these changes I was able to achieve a smooth UI with multiple (2) video cells on the screen at a time. Hope this helps and let me know if you have any specific questions or if what I described wasn't clear.