What do I need to record from my TV straight to my laptop?

I see it often with Youtube videos where people upload videos of themselves playing a video game. They obviously didn't record the screen with their cell phone. They were able to record straight from their TV in HD quality.


How would I do such a thing?


I'm switching from Dish Network to Comcast a week from today, and I have a couple things recorded that I'd like to keep, and I figured this would be the best way since you cannot transfer DVR recordings from one company to another.