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POIssue with setting and retrieving the value of AVMetadataCommonKeyCreator
 

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  1. POIssue with setting and retrieving the value of AVMetadataCommonKeyCreator
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    <p>I have a video recording app for the iPhone. I am using <code>AVAssetWriter</code> for writing the recorded video data to a file. I am also interested in embedding custom metadata to the file. For eg: I want to identify my application as the creator of the video.</p> <p>Hence after creating the asset writer, I am adding the creator value using the key <code>AVMetadataCommonKeyCreator</code> to the metadata of the asset writer.</p> <p>Code snippet is as follows:</p> <pre><code>AVAssetWriter *assetWrtr = [[AVAssetWriter alloc] initWithURL:inURL fileType:AVFileTypeQuickTimeMovie error:&amp;error]; self.assetWriter = assetWrtr; [assetWrtr release]; NSArray *existingMetadataArray = self.assetWriter.metadata; NSMutableArray *newMetadataArray = nil; if (existingMetadataArray) { newMetadataArray = [existingMetadataArray mutableCopy]; // To prevent overriding of existing metadata } else { newMetadataArray = [[NSMutableArray alloc] init]; } AVMutableMetadataItem *item = [[AVMutableMetadataItem alloc] init]; item.keySpace = AVMetadataKeySpaceCommon; item.key = AVMetadataCommonKeyCreator; item.value = @"My App"; [newMetadataArray addObject:item]; self.assetWriter.metadata = newMetadataArray; [newMetadataArray release]; [item release]; </code></pre> <p>Once the recording is done, I am trying to read the contents of the file using AVURLAsset.</p> <pre><code>NSURL *outputFileURL = [self.assetWriter outputURL]; AVURLAsset *asset = [AVURLAsset URLAssetWithURL:outputFileURL options:nil]; NSArray *keys = [NSArray arrayWithObject:@"commonMetadata"]; [asset loadValuesAsynchronouslyForKeys:keys completionHandler:^(void) { NSError *error = nil; AVKeyValueStatus durationStatus = [asset statusOfValueForKey:@"commonMetadata" error:&amp;error]; switch (durationStatus) { case AVKeyValueStatusLoaded: NSLog(@"AVKeyValueStatusLoaded"); NSLog(@"commonMetadata:%@", [asset commonMetadata]); break; case AVKeyValueStatusFailed: NSLog(@"AVKeyValueStatusFailed"); break; case AVKeyValueStatusCancelled: NSLog(@"AVKeyValueStatusCancelled"); break; } }]; </code></pre> <p>However <code>[asset commonMetadata]</code> does not return any <code>AVMetadataItems</code>. It returns an empty array. I am able to set the values of other meta data objects like <code>AVMetadataCommonKeyTitle</code>, <code>AVMetadataCommonKeyModel</code>, <code>AVMetadataCommonKeySource</code>. These values are retrieved properly. The problem is only with <code>AVMetadataCommonKeyCreator</code>. Please let me know the reason for this behavior. Is it not possible to set app specific value for <code>AVMetadataCommonKeyCreator</code>? What does this key actually represent?</p>
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