AVAssetExportSession Trim &下载

Question

我正在尝试使用AVExportSession来修剪和下载在线视频。

代码：

FileMove *fileMove = (FileMove*)data;
  NSString *url = @"http://download.wavetlan.com/SVV/Media/HTTP/H264/Talkinghead_Media/H264_test1_Talkinghead_mp4_480x360.mp4";
    NSURL *videoURL = [NSURL URLWithString:[url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
    NSLog(@"VideoURL: %@",videoURL);


    AVAsset *anAsset = [AVURLAsset URLAssetWithURL:videoURL options:nil];    
    NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:anAsset];
    if ([compatiblePresets containsObject:AVAssetExportPresetLowQuality]) {
        AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]
                                               initWithAsset:anAsset presetName:AVAssetExportPresetLowQuality];
        NSURL *outputURL = [NSURL fileURLWithPath:fileMove.dst];
        NSLog(@"outputURL: %@",outputURL);
        exportSession.outputURL = outputURL;
        exportSession.outputFileType = AVFileTypeQuickTimeMovie;

        CMTime start = CMTimeMakeWithSeconds(1.0, 600);
        CMTime duration = CMTimeMakeWithSeconds(3.0, 600);
        CMTimeRange range = CMTimeRangeMake(start, duration);
        exportSession.timeRange = range;

        if ([[NSFileManager defaultManager] fileExistsAtPath:fileMove.dst])
            [[NSFileManager defaultManager] removeItemAtPath:fileMove.dst error:nil];

        [exportSession exportAsynchronouslyWithCompletionHandler:^{

            switch ([exportSession status]) {
                case AVAssetExportSessionStatusFailed:
                    NSLog(@"Export failed: %@", [[exportSession error]description ]);
                    break;
                case AVAssetExportSessionStatusCancelled:
                    NSLog(@"Export canceled");
                    break;
                default:
                    break;
            }
        }];
    }

错误：

导出失败:错误Domain=AVFoundationErrorDomain代码=-11800“操作无法完成”UserInfo=0x635a820 {NSLocalizedDescription=The操作无法完成，NSUnderlyingError=0x1ff4240“操作无法完成。(OSStatus错误-12780.)"，NSLocalizedFailureReason=An未知错误(-12780)}

你们看到密码里有什么问题吗？AVExportSession访问在线视频有什么限制吗？

Answer 1

我已经成功地使用AVFoundation修剪了远程视频。下面是用Swift编写的示例代码：

let range: CMTimeRange
let sourceURL: NSURL
let targetFileURL: NSURL
let requiredKeys = [ "exportable", "tracks" ]
let asset = AVAsset(URL: sourceURL)
asset.loadValuesAsynchronouslyForKeys(requiredKeys) {

    // Error handling code here
    precondition(asset.statusOfValueForKey("exportable", error: nil) == .Loaded)
    precondition(asset.statusOfValueForKey("tracks", error: nil) == .Loaded)
    precondition(asset.exportable)


    let composition = AVMutableComposition()
    do {
        try composition.insertTimeRange(range, ofAsset: asset, atTime: kCMTimeZero)
    } catch {
        // Error handling code here
        return
    }

    let finalComposition = composition.copy() as! AVComposition
    guard let export = AVAssetExportSession(asset: finalComposition, presetName: AVAssetExportPresetPassthrough) else {
        // Error handling code here
        return
    }

    export.outputURL = targetFileURL
    export.outputFileType = AVFileTypeMPEG4
    export.exportAsynchronouslyWithCompletionHandler {
        switch export.status {
        case .Completed:
            // Alright!
            break

        case .Cancelled, .Failed:
            // Error handling code here
            break

        default:
            fatalError("Shouldn't be called")
        }
    }
}

Answer 2

用于创建AVAsset的URL需要是您可以访问的本地文件。在创建AVAsset like so之前，您需要将其下载到设备上。

Answer 3

我认为我们无法输出在线视频参见：Unable to export AVPlayerItem

所以我想，你可以先在本地下载视频，然后修剪，保存和使用它。