Picture in picture is an old technology and yes if you wanted to use that same technolgy today it would take 2 cable boxes. But the pip feature, the end result is completely do-able. A common hd tv , with hdmi input is basically a computer screen and a computer screen can have 2 or more streaming videos running at once. But just like many features and common sense capabilities that used to be in older technology, the x1 developers apparently didnt do a quality comparison to asure they were going forward instead if backwards. Or even more probable, comcast was too cheap or lazy to put this nice feature in. But it could be done, and with one box.