AVAssetExportSession exportAsynchronouslyWithCompletionHandler返回失败

Question

我正在实现AVAssetExportSession，以修剪一个在线视频，但总是返回失败。

以下是我的实现：

NSString *url = @"http://www.ebookfrenzy.com/ios_book/movie/movie.mov";
NSURL *fileURL = [NSURL URLWithString:url];
AVAsset *asset = [AVAsset assetWithURL:fileURL];
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetHighestQuality];
NSURL *exportUrl = [NSURL fileURLWithPath:[documentsDirectory stringByAppendingPathComponent:@"export.m4a"]];

exportSession.outputURL = exportUrl;
exportSession.outputFileType = AVFileTypeQuickTimeMovie;
CMTime time = CMTimeMake(1, 10);
exportSession.timeRange = CMTimeRangeMake(kCMTimeZero, time);
[exportSession exportAsynchronouslyWithCompletionHandler:^(void) {

    switch (exportSession.status)
    {
        case AVAssetExportSessionStatusCompleted:
            /*expor is completed*/
            NSLog(@"Completed!!");
            break;
            case AVAssetExportSessionStatusFailed:
            NSLog(@"failed!!");
            /*failed*/
            break;
        default:
            break;
    }
}];

你们知道为什么会发生这种事或者我做错了什么吗？

Answer 1

您正在尝试使用远程URL创建一个AVAsset，并且在开始导出之前，您需要知道资产已经加载。

AVAsset符合AVAsynchronousKeyValueLoading协议，这意味着一旦值发生变化，您就可以观察tracks密钥并启动导出：

NSURL *myURL = [NSURL URLWithString:myMovieURLString];
AVAsset *asset = [AVAsset assetWithURL:myURL];

__weak typeof(self) weakSelf = self;

[asset loadValuesAsynchronouslyForKeys:@[@"tracks"] completionHandler:^{

    //Error checking here - make sure there are tracks

    [weakSelf exportAsset:asset];

}];

然后，您可以将导出代码放在单独的方法中：

- (void)exportAsset:(AVAsset *)asset {

    //Your export code here
}

Answer 2

documentsDirectory应该是一条退出路径。如果没有，exportSession.status将等于AVAssetExportSessionStatusFailed