my ps3 keeps freezing every 20mins?

when i load call of duty, more importantly black ops 2 it freezes everytime i start a map or even while in the map. i played gta for an hour and battlefield for 30mins and it never froze once but when i put in black ops 2 it freezes. i need gamepllays for my youtube channel and i cant record if it freezes. what do i do?