Shareable mp4 file URL

+ (NSURL *)uniqueMp4URL
{
    NSString *path = [NSTemporaryDirectory() stringByAppendingPathComponent:ClipDirectory];
    if (![[NSFileManager defaultManager] createDirectoryAtPath:path withIntermediateDirectories:YES attributes:nil error:nil])
    {
        NSLog(@"Unable to create clip directory");
    }
    
    NSString *uniqueString = [[NSProcessInfo processInfo] globallyUniqueString];
    path = [path stringByAppendingPathComponent:uniqueString];
    
    NSString *pathExtension = CFBridgingRelease(UTTypeCopyPreferredTagWithClass((CFStringRef)AVFileTypeMPEG4, kUTTagClassFilenameExtension));
    path = [path stringByAppendingPathExtension:pathExtension];
    
    return [NSURL fileURLWithPath:path];
}