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AVAssetExportSession 输出文件应该是什么样子？我正在尝试从 ALAsset 项目压缩视频，但它不起作用。我猜输出文件与它有关。

这是我正在使用的代码：

NSString *destinationPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Movie"];
[self convertVideoToLowQualityWithInputURL:asset.defaultRepresentation.url outputURL:[NSURL URLWithString:destinationPath]];

- (void)convertVideoToLowQualityWithInputURL:(NSURL*)inputURL outputURL:(NSURL*)outputURL {

    if([[NSFileManager defaultManager] fileExistsAtPath:[NSString stringWithContentsOfURL:outputURL encoding: 0 error:Nil]]) [[NSFileManager defaultManager] removeItemAtURL:outputURL error:nil];

    AVURLAsset *assetAV = [AVURLAsset URLAssetWithURL:inputURL options:nil];

    NSLog(@"url string from asset: %@", assetAV.URL);
    NSLog(@"output url: %@", [outputURL absoluteString]);

    [[NSFileManager defaultManager] createFileAtPath:[outputURL path] contents:nil attributes:nil];

    NSLog(@"duration: %lld", assetAV.duration.value); //it logs a valid value, so it's all good so far

    AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:assetAV presetName:AVAssetExportPresetLowQuality];
    exportSession.outputURL = outputURL;
    exportSession.outputFileType = AVFileTypeQuickTimeMovie;
    [exportSession exportAsynchronouslyWithCompletionHandler:^(void) {
        if (exportSession.status == AVAssetExportSessionStatusCompleted) {
            NSLog(@"success");
        } else {
            NSLog(@"error: %@", [exportSession error]);
            //error: Error Domain=AVFoundationErrorDomain Code=-11800 "The operation could not be completed" UserInfo=0x2023b720 {NSLocalizedDescription=The operation could not be completed, NSUnderlyingError=0x2023bb70 "The operation couldn’t be completed. (OSStatus error -12780.)", NSLocalizedFailureReason=An unknown error occurred (-12780)}
        }
    }];
}

有人可以帮帮我吗？

更新：

找到了解决方案。我认为问题出在输出文件上，所以这里是生成有效文件的代码：

            NSUInteger count = 0;
            NSString *filePath = nil;
            do {
                NSString *extension = ( NSString *)UTTypeCopyPreferredTagWithClass(( CFStringRef)AVFileTypeQuickTimeMovie, kUTTagClassFilenameExtension);
                NSString *fileNameNoExtension = [[asset.defaultRepresentation.url URLByDeletingPathExtension] lastPathComponent];
                NSString *fileName = [NSString stringWithFormat:@"%@-%@-%u",fileNameNoExtension , AVAssetExportPresetLowQuality, count];
                filePath = NSTemporaryDirectory();
                filePath = [filePath stringByAppendingPathComponent:fileName];
                filePath = [filePath stringByAppendingPathExtension:extension];
                count++;

            } while ([[NSFileManager defaultManager] fileExistsAtPath:filePath]);

            NSURL *outputURL = [NSURL fileURLWithPath:filePath];
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1 回答 1

19

您的问题是 [NSURL URLWithString:destinationPath] 仅此而已。您需要像在解决方案中那样使用 [NSURL fileURLWithPath:xxx]。发布此内容只是为了澄清这是唯一的问题。

于 2013-08-26T11:16:52.220 回答