How to stream a video with AVURLAsset and save to disk the cached data

Question

Some days ago I was asked to check how difficult is to play a video while downloading it from Internet. I know it\'s an easy task because someone told me a while ago. So, I

Answer 1

The team at Calm has open-sourced our implementation to this. It's available as a CocoaPod. It's called PersistentStreamPlayer.

Features include:

• streaming of audio file, starting playback as soon as first data is available
• also saves streamed data to a file URL as soon as the buffer completes exposes timeBuffered, helpful for displaying buffer progress bars in the UI
• handles re-starting the audio file after the buffer stream stalls (e.g. slow network)
• simple play, pause and destroy methods (destroy clears all memory resources)
• does not keep audio file data in memory, so that it supports large files that don't fit in RAM

You can find it here: https://github.com/calmcom/PersistentStreamPlayer

Answer 2

The solution for this problem is to use AVAssetExportSession and AVAssetResourceLoaderDelegate:

First step is to add a notification to know when the video finish. Then we can start saving it to disk.

override func viewDidLoad() {

    super.viewDidLoad()

    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(playerItemDidReachEnd(_:)), name: AVPlayerItemDidPlayToEndTimeNotification, object: nil)

    ...
}

deinit {

    NSNotificationCenter.defaultCenter().removeObserver(self)
}

The implementation of our function:

func playerItemDidReachEnd(notification: NSNotification) {

    if notification.object as? AVPlayerItem  == player.currentItem {

        let exporter = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetHighestQuality)

        let filename = "filename.mp4"

        let documentsDirectory = NSFileManager.defaultManager().URLsForDirectory(NSSearchPathDirectory.DocumentDirectory, inDomains: NSSearchPathDomainMask.UserDomainMask).last!

        let outputURL = documentsDirectory.URLByAppendingPathComponent(filename)

        exporter?.outputURL = outputURL
        exporter?.outputFileType = AVFileTypeMPEG4

        exporter?.exportAsynchronouslyWithCompletionHandler({

            print(exporter?.status.rawValue)
            print(exporter?.error)
        })
    }
}

Finally we need to make our AVURLAsset delegate of AVAssetResourceLoaderDelegate:

lazy var asset: AVURLAsset = {

    var asset: AVURLAsset = AVURLAsset(URL: self.url)

    asset.resourceLoader.setDelegate(self, queue: dispatch_get_main_queue())

    return asset
}()

And:

extension ViewController : AVAssetResourceLoaderDelegate {

}

I created a small demo with this code in GitHub.