How do I convert NSData to file format (.mp4/.m4a)

Question

I have some NSData variables which contain .m4a / .mp4 file formats. I've tried looking at ways to convert the NSData into file format, with no luck. I need to convert it into a file, change some of it's metadata, and convert it back to NSData . Here's some code:

// This JSON basically gets the url of a .m4a
NSArray *preview = [JSON valueForKeyPath:@"results.previewUrl"];

_previewData = [NSMutableData dataWithContentsOfURL:[NSURL URLWithString:[preview objectAtIndex:0]]];

[_previewData writeToFile:path atomically:YES];
    ANMovie* file = [[ANMovie alloc] initWithFile:_previewData]; // or .mp4
    NSData* jpegCover = UIImageJPEGRepresentation(artworkImage, 1.0);
    ANMetadata* metadata = [[ANMetadata alloc] init];
    metadata.albumCover = [[ANMetadataImage alloc] initWithImageData:jpegCover type:ANMetadataImageTypeJPG];
    [file setMovieMetadata:metadata];
    [file close];

Answer 1

I'm guessing [[ANMovie alloc] initWithFile:] expects a file, and you've passed it, I'm also assuming here, an NSData* .

Try:

ANMovie* file = [[ANMovie alloc] initWithFile:path];