IOS How to write and read Metadata to video? - ios

Question

I'm trying to write Metadata information inside a Video recorded inside my app. At the end of video taking i have:
NSMutableArray *metadata = [NSMutableArray array];
AVMutableMetadataItem *mi = [AVMutableMetadataItem metadataItem];
mi.key = AVMetadataCommonKeyTitle;
mi.keySpace = AVMetadataKeySpaceCommon;
mi.value = #"testmetadata";
[metadata addObject:mi];
AVMutableMetadataItem *mi2 = [AVMutableMetadataItem metadataItem];
mi2.key = AVMetadataCommonKeyIdentifier;
mi2.keySpace = AVMetadataKeySpaceCommon;
mi2.value = #"testmetadata";
[metadata addObject:mi2];
AVURLAsset *asset = [AVURLAsset URLAssetWithURL:self.outputURL options:nil];
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:asset presetName:AVAssetExportPresetHighestQuality];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *outputURL_nuovo = paths[0];
NSFileManager *manager = [NSFileManager defaultManager];
[manager createDirectoryAtPath:outputURL_nuovo withIntermediateDirectories:YES attributes:nil error:nil];
outputURL_nuovo = [outputURL_nuovo stringByAppendingPathComponent:#"output.mp4"];
// Remove Existing File
[manager removeItemAtPath:outputURL_nuovo error:nil];
exportSession.outputURL = [NSURL fileURLWithPath:outputURL_nuovo];
exportSession.shouldOptimizeForNetworkUse = YES;
exportSession.outputFileType = AVFileTypeQuickTimeMovie;
exportSession.metadata=metadata;
CMTime start = CMTimeMakeWithSeconds(1.0, 600);
CMTime duration = CMTimeMakeWithSeconds(3.0, 600);
CMTimeRange range = CMTimeRangeMake(start, duration);
exportSession.timeRange = range;
[exportSession exportAsynchronouslyWithCompletionHandler:^(void)
{
switch (exportSession.status) {
case AVAssetExportSessionStatusCompleted:
[self writeVideoToPhotoLibrary:[NSURL fileURLWithPath:outputURL_nuovo]];
NSLog(#"Export Complete %d %#", exportSession.status, exportSession.error);
break;
case AVAssetExportSessionStatusFailed:
NSLog(#"Failed:%#",exportSession.error);
break;
case AVAssetExportSessionStatusCancelled:
NSLog(#"Canceled:%#",exportSession.error);
break;
default:
break;
}
}];
If the export end with success, i have this other method:
-(void)writeVideoToPhotoLibrary: (NSURL*)url{
ALAssetsLibrary* assetsLibrary = [[ALAssetsLibrary alloc] init];
[assetsLibrary writeVideoAtPathToSavedPhotosAlbum:url
completionBlock:^(NSURL *assetURL, NSError *error)
{
[assetsLibrary assetForURL:assetURL resultBlock:^(ALAsset *asset) {
ALAssetRepresentation *assetRep = [asset defaultRepresentation];
NSLog(#"Image filename: %#", [assetRep filename]);
NSDate *date = [asset valueForProperty:ALAssetPropertyDate];
NSLog(#"DATA prima %#",date);
NSLog(#"TIMESTAMP %f",[date timeIntervalSince1970]);
//////////get info
[assetsLibrary assetForURL:url resultBlock:^(ALAsset *asset) {
ALAssetRepresentation *assetRep = [asset defaultRepresentation];
NSLog(#"Image filename dopp: %#", [assetRep filename]);
NSLog(#"METADATA %#",[assetRep metadata]);
} failureBlock:^(NSError *error) {
NSLog(#"Error: %#", error.localizedDescription);
}];
///////////////get info
} failureBlock:^(NSError *error) {
NSLog(#"Error: %#", error.localizedDescription);
}];
}];
}
With this code i'm trying to save a video with some metadata in it, like a title, and then read the metadata i've just saved. The log returns a null value METADATA (null) , what i'm doing wrong?