How can I use AVAssetExportSession to overwrite songs in my iPhone/iPod library?

Question

So supposedly in the iOS 4 SDK you can edit and write to the user's iTunes library. I can successfully load an AVAsset from my iPhone/iPod library, but as a quick test I'm trying to just overwrite the same file right away using AVAssetExportSession but it's always returning the status "4" which I THINK is AVAssetExportSessionStatusFailed... In the documentation it says:

enum {
    AVAssetExportSessionStatusUnknown,
    AVAssetExportSessionStatusExporting,
    AVAssetExportSessionStatusCompleted,
    AVAssetExportSessionStatusFailed,
    AVAssetExportSessionStatusCancelled,
    AVAssetExportSessionStatusWaiting
};

but in AVAssetExportSession.h it says:

enum {
    AVAssetExportSessionStatusUnknown,
    AVAssetExportSessionStatusWaiting,
    AVAssetExportSessionStatusExporting,
    AVAssetExportSessionStatusCompleted,
    AVAssetExportSessionStatusFailed,
    AVAssetExportSessionStatusCancelled
};
typedef NSInteger AVAssetExportSessionStatus;

Here's the code I'm using:

// before this, i'm using mpmediapicker to pick an m4a file i synched with my itunes library 

NSURL *assetUrl = [[self.userMediaItemCollection.items objectAtIndex: 0] valueForProperty: MPMediaItemPropertyAssetURL];
AVURLAsset *asset = [AVURLAsset URLAssetWithURL: assetUrl options: nil];
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset: asset presetName: AVAssetExportPresetAppleM4A];
exportSession.outputURL = asset.URL;
exportSession.outputFileType = AVFileTypeAppleM4A;

NSLog(@"output filetype: %@", exportSession.outputFileType);
// prints "com.apple.m4a-audio"

[exportSession exportAsynchronouslyWithCompletionHandler: ^(void) {
    NSLog(@"status: %i for %@", exportSession.status, exportSession.outputURL);
    // prints "status: 4 for ipod-library://item/item.m4a?id=3631988601206299774"
}];

[exportSession release];

So either way... I guess it's "failed" or "cancelled." Has anyone else successfully written to the media library before?

Thanks!

Answer 1

you cannot write to itunes library, only read from it now.

Answer 2

ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
NSParameterAssert(library);
if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:[NSURL     fileURLWithPath:movieFileName]]) {
   [library writeVideoAtPathToSavedPhotosAlbum:[NSURL fileURLWithPath:movieFileName]     completionBlock:^(NSURL *assetURL, NSError *error){}];
}
[library release];