同步将PHAsset(视频)转换为AVAsset

Question

我需要使用AVAsset对象,以便使用AVPlayer和AVPlayerLayer播放它.我开始使用Photos框架,因为不推荐使用AssetsLibrary.现在我到了我有一个PHAsset对象数组的点,我需要将它们转换为AVAsset.我尝试通过PHFetchResult枚举并使用PHAsset的本地化描述分配新的AVAsset,但是当我播放时它似乎没有显示任何视频.

    PHAssetCollection *assetColl = [self scaryVideosAlbum];

    PHFetchResult *getVideos = [PHAsset fetchAssetsInAssetCollection:assetColl options:nil];

    [getVideos enumerateObjectsUsingBlock:^(PHAsset *asset, NSUInteger idx, BOOL *stop) {
            NSURL *videoUrl = [NSURL URLWithString:asset.localizedDescription];
            AVAsset *avasset = [AVAsset assetWithURL:videoUrl];
            [tempArr addObject:avasset];
    }];

我假设本地化描述不是视频的绝对URL.

我还偶然发现了PHImageManager和requestAVAssetForVideo,但是,当涉及到视频时,options参数没有isSynchrounous属性,image参数就是这种情况.

        PHVideoRequestOptions *option = [PHVideoRequestOptions new];
        [[PHImageManager defaultManager] requestAVAssetForVideo:videoAsset options:option resultHandler:^(AVAsset * _Nullable avasset, AVAudioMix * _Nullable audioMix, NSDictionary * _Nullable info) {

有同步方法吗？

谢谢.

Answer 1

不,没有.但是你可以构建一个同步版本:

dispatch_semaphore_t    semaphore = dispatch_semaphore_create(0);

PHVideoRequestOptions *option = [PHVideoRequestOptions new];
__block AVAsset *resultAsset;

[[PHImageManager defaultManager] requestAVAssetForVideo:videoAsset options:option resultHandler:^(AVAsset * avasset, AVAudioMix * audioMix, NSDictionary * info) {
    resultAsset = avasset;
    dispatch_semaphore_signal(semaphore);
}];

dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
// yay, we synchronously have the asset
[self doSomethingWithAsset:resultAsset];

但是,如果您在主线程上执行此操作并且requestAVAssetForVideo:耗时太长,则可能会锁定UI或甚至被iOS监视程序终止.

使用异步回调版本重写您的应用程序可能更安全.像这样的东西:

__weak __typeof(self) weakSelf = self;

[[PHImageManager defaultManager] requestAVAssetForVideo:videoAsset options:option resultHandler:^(AVAsset * avasset, AVAudioMix * audioMix, NSDictionary * info) {
    dispatch_async(dispatch_get_main_queue(), ^{
        [weakSelf doSomethingWithAsset:avasset];
    });
}];

Answer 2

对于Swift 2,您可以PHAsset使用以下方法轻松播放视频,

导入文件

import AVKit

来自PHAsset

static func playVideo (view:UIViewController, asset:PHAsset) {

        guard (asset.mediaType == PHAssetMediaType.Video)

            else {
                print("Not a valid video media type")
                return
        }

        PHCachingImageManager().requestAVAssetForVideo(asset, options: nil, resultHandler: {(asset: AVAsset?, audioMix: AVAudioMix?, info: [NSObject : AnyObject]?) in

            let asset = asset as! AVURLAsset

            dispatch_async(dispatch_get_main_queue(), {

                let player = AVPlayer(URL: asset.URL)
                let playerViewController = AVPlayerViewController()
                playerViewController.player = player
                view.presentViewController(playerViewController, animated: true) {
                    playerViewController.player!.play()
                }
            })
        })
    }