How to reproduce assets at the same time

AVURLAssetLoading.m

AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:url options:nil];
NSArray *keys = [NSArray arrayWithObject:@"playable"];

//Carga los assets
[asset loadValuesAsynchronouslyForKeys:keys completionHandler:^()
{
    //Al terminar reproducelos en la cola principal
    dispatch_async(dispatch_get_main_queue(), ^
    {
        AVPlayerItem *playerItem = [[[AVPlayerItem alloc] initWithAsset:asset] autorelease];         
        [player insertItem:playerItem afterItem:nil]; 
    });
}];