Issue playing slow-mo AVAsset in AVPlayer

问题

I'm trying to play an slow motion video (filmed by the user's iPhone) in an AVPlayer.

I am retrieving the AVAsset with a request on a PHAsset from a picker:

   [manager requestAVAssetForVideo:PHAsset
                           options:videoRequestOptions
                     resultHandler:^(AVAsset * avasset, AVAudioMix * audioMix, NSDictionary * info) {}];

The problem is once it plays, I get this error:

 -[AVComposition URL]: unrecognized selector sent to instance 0x138d17f40

However, if I set this option on the manager request, it will play as normal speed video at 120/240fps and no crashes:

  videoRequestOptions.version = PHVideoRequestOptionsVersionOriginal;

Whats going on? The default version property is PHVideoRequestOptionsVersionCurrent which incorporates slow motion, user edits and trims, etc.

I would like to play that video version. Thanks

回答1:

So it turns out that slow motion videos are passed as AVComposition.

You can export that into a video file / URL, and then handle it like any other video.

Solution here: https://overflow.buffer.com/2016/02/29/slow-motion-video-ios/

//Output URL
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = paths.firstObject;
NSString *myPathDocs =  [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"mergeSlowMoVideo-%d.mov",arc4random() % 1000]];
NSURL *url = [NSURL fileURLWithPath:myPathDocs];

//Begin slow mo video export
AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetHighestQuality];
exporter.outputURL = url;
exporter.outputFileType = AVFileTypeQuickTimeMovie;
exporter.shouldOptimizeForNetworkUse = YES;

[exporter exportAsynchronouslyWithCompletionHandler:^{
    dispatch_async(dispatch_get_main_queue(), ^{
        if (exporter.status == AVAssetExportSessionStatusCompleted) {
            NSURL *URL = exporter.outputURL;
            NSData *videoData = [NSData dataWithContentsOfURL:URL];

             // Upload
             [self uploadSelectedVideo:video data:videoData];
         }
    });
}];

回答2:

For those coming here looking for a swift answer, this is the swift translation, which I use in my project, where I need the url of the slow-motion Video to play it with the AVPlayerViewController:

else if asset is AVComposition {
//Slow-Motion Assets are passed as AVComposition
let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
let documentsDirectory: NSString? = paths.first as NSString?
if documentsDirectory != nil {
    let random = Int(arc4random() % 1000)
    let pathToAppend = String(format: "mergeSlowMoVideo-%d.mov", random)
    let myPathDocs = documentsDirectory!.strings(byAppendingPaths: [pathToAppend])
    let myPath = myPathDocs.first
    if myPath != nil {
        let url = URL(fileURLWithPath: myPath!)
        let exporter = AVAssetExportSession(asset: asset!, presetName: AVAssetExportPresetHighestQuality)
        if exporter != nil {
        exporter!.outputURL = url
        exporter!.outputFileType = AVFileTypeQuickTimeMovie
        exporter!.shouldOptimizeForNetworkUse = true
        exporter!.exportAsynchronously(completionHandler: {
            AsyncUtil.asyncMain {
                let url = exporter!.outputURL
                if url != nil {
                    let player = AVPlayer(url: url!)
                    let playerViewController = AVPlayerViewController()
                    playerViewController.player = player
                    playerViewController.modalTransitionStyle = .crossDissolve
                    view.present(playerViewController, animated: true) {
                        playerViewController.player!.play()
                    }
                }
            }
        })
    }
}

来源：https://stackoverflow.com/questions/36961891/issue-playing-slow-mo-avasset-in-avplayer