AVAssetExportSession Trimmed Audio显示错误的持续时间元数据iOS7

Question

我正在使用https://developer.apple.com/library/ios/qa/qa1730/_index.html#//apple_ref/doc/uid/DTS40010629处的代码修剪音频，直到iOS 7更新才有效。媒体被裁剪到正确的持续时间并且如此播放但是当在iTunes中观看时，裁剪的剪辑显示出与原始音频文件相同的持续时间元数据。任何帮助将不胜感激。感谢。

更新：

AVMutableMetadataItem *titleMetadata = [[AVMutableMetadataItem alloc] init];
titleMetadata.keySpace = AVMetadataKeySpaceCommon;
titleMetadata.key = AVMetadataCommonKeyTitle;
titleMetadata.value = @"Title";

AVMutableMetadataItem *durationMetadata = [[AVMutableMetadataItem alloc] init];
durationMetadata.keySpace = AVMetadataKeySpaceID3;
durationMetadata.key = AVMetadataID3MetadataKeyLength;
durationMetadata.value = [NSNumber numberWithDouble:30.0];


NSArray *metadeta = [[NSArray alloc] initWithObjects:titleMetadata,durationMetadata, nil];

exporter.metadata = metadeta;