Question

使用新的Photo框架，我可以使用NSData访问requestImageDataForAsset个PHAssets。我还可以使用返回的PHImageFileURLKey的{{1}}访问文件网址。

info NSDictionary

这适用于图像和普通视频。

但是，当资产是PHAssetMediaSubtypeVideoHighFrameRate（慢动作视频）时，返回的数据对应于包含视频第一帧的JPG文件（NSData，dataUTI和信息字典都指向同一个jpg文件）。例如，这是为慢动作视频返回的URL和dataUTI：

PHImageFileURLKey = “文件：///var/mobile/Media/PhotoData/Metadata/DCIM/100APPLE/IMG_0642.JPG”; PHImageFileUTIKey =“public.jpeg”;

为什么会这样？如何访问慢动作视频的NSData / NSURL而不是JPG预览？

Answer 1

疯狂地测试每一个选项之后我发现了问题。

为慢动作视频返回JPG图像的责任是PHImageRequestOptionsVersionCurrent属性的默认PHImageRequestOptions.version值。

只需将版本分配给PHImageRequestOptionsVersionUnadjusted或PHImageRequestOptionsVersionOriginal将返回原始慢动作视频。

PHImageRequestOptions * imageRequestOptions = [[PHImageRequestOptions alloc] init];

imageRequestOptions.version = PHImageRequestOptionsVersionUnadjusted;
// or 
imageRequestOptions.version = PHImageRequestOptionsVersionOriginal;

我认为这是一种意想不到的行为，因为我不期望慢动作视频的“当前”版本是静止图像（可能是应用了慢动作效果的视频，而不是照片）。

希望这对某人有用。

Answer 2

重要的是要注意慢动作视频的类型为AVComposition而不是AVURLAsset。 AVComposition对象将来自多个源的媒体数据组合在一起。

导出慢动作视频

为实现这一目标，我基本上经历了一个三步过程：

为视频
配置导出会话
导出视频并抓取网址！

PHVideoRequestOptions *options = [PHVideoRequestOptions new];
        options.networkAccessAllowed = YES;
        [[PHImageManager defaultManager] requestAVAssetForVideo:asset options:options resultHandler:^(AVAsset *asset, AVAudioMix *audioMix, NSDictionary *info) {
            if(([asset isKindOfClass:[AVComposition class]] && ((AVComposition *)asset).tracks.count == 2)){
                //slow motion videos. See Here: https://overflow.buffer.com/2016/02/29/slow-motion-video-ios/

                //Output URL of the slow motion file.
                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;
                            self.filePath=URL.absoluteString;



                            // NSData *videoData = [NSData dataWithContentsOfURL:URL];
                            //
                            //// Upload
                            //[self uploadSelectedVideo:video data:videoData];
                        }
                    });
                }];


            } 
        }];

请在iOS中查看这个精彩的blog慢动作视频。

Answer 3

以下是Swift 3/4的代码段

PHImageManager.default().requestAVAsset(forVideo: asset, 
                                         options: nil, 
                                         resultHandler: { (asset, _, _) in

            // AVAsset has two sub classes: AVComposition and AVAssetURL
            // AVComposition for slow mo vid
            // AVAssetURL for normal videos

            // For slow motion video checking for AVCompostion
            // Creating an exporter to write the video into local file path and using the same to play/upload

            if asset!.isKind(of: AVComposition.self){

                let avCompositionAsset = asset as! AVComposition

                if avCompositionAsset.tracks.count > 1{

                    let exporter = AVAssetExportSession(asset: avCompositionAsset, presetName: AVAssetExportPresetHighestQuality)
                    exporter!.outputURL = self.fetchOutputURL()
                    exporter!.outputFileType = AVFileTypeMPEG4
                    exporter!.shouldOptimizeForNetworkUse = true

                    exporter!.exportAsynchronously {
                        DispatchQueue.main.sync {
                          // Use this url for uploading or playing a video
                           let url = exporter!.outputURL
                        }
                    }
                }
            }else{

                // Normal video, are stored as AVAssetURL

                let url = (asset as! AVURLAsset).url
            }
        })

// Fetch local path

 func fetchOutputURL() -> URL{
     let documentDirectory = getDocumentsDirectory() as NSString
     let path = documentDirectory.appendingPathComponent("test.mp4")
     return URL(fileURLWithPath:path)
 }

Answer 4

// video slo-mo

PHVideoRequestOptions *options=[[PHVideoRequestOptions alloc]init];
options.version=PHVideoRequestOptionsVersionOriginal;

从PHImageManager请求AVAsset

[[PHImageManager defaultManager] requestAVAssetForVideo:videoAsset options:options resultHandler:^(AVAsset *asset, AVAudioMix *audioMix, NSDictionary *info)
 {         
     if ([asset isKindOfClass:[AVURLAsset class]])
     {
         // use URL to get file content

         NSURL *URL = [(AVURLAsset *)asset URL];
         NSData *videoData=[NSData dataWithContentsOfURL:URL];
         NSNumber *fileSizeValue = nil;
         [URL getResourceValue:&fileSizeValue forKey:NSURLFileSizeKey error:nil];
      }
}

如何使用PhotoKit访问NSData / NSURL的慢动作视频

4 个答案:

导出慢动作视频