Another thing to consider, if you have 21 rows, and each row has 4000 items, how would your users be able to locate what they want?
Even with 10 displayed items on the screen at once, do you think the end user will appreciate being forced to hit fast forward or rewind on their remote a maximum of 200 times (10 times to get to row item #200, and times that by 10 to get to row item #2000, to select a video?  What kind of user experience are you making them suffer through to do that?  Even if you are only loading 10 things at a time that just sounds like a bad way of doing it when you could use sub-categories and secondary screens or a search feature and better organization to save valuable time.  For each of your 21 rows that is still excessive.