I took a video of a TV, and I want to crop it so that only the TV is in the video. My problem is that since my phone wasn't facing the TV at a perfect 90 degree angle, I can't simply crop it like a rectangle. Is there any way I can crop it so that I can set the corners? This is similar to how scanner apps on smartphones work. You set the corners and it makes it look like you are directly looking at it. Sorry for my mediocre explanation. The app Genius Scan utilizes what I'm talking about.
Yes, you can. If you're in Final Cut Pro X you can use the "Distort" section of the inspector, or in Motion, you can use the "Four Corner" function in the Inspector when your video is selected. (In Motion it will be in the Properties tab.) The same functionality is available via the on-screen controls, which are easier to use than entering values by hand.
I believe that After Effects and Premiere have similar functionality, though I don't remember the details off the top of my head as it's been a few years since I used them regularly.