Hello everyone, my name is Daniel and I'm a College student into a Programming course.
There, presentation handled. Now the actual thing
This semester we're working with Arduino and I got a Project in mind for my last semester.
Basically is making kind of a play/pause controller for music/video files(independent of it is either a file on your computer or if it is running in something like Spotify, QuickTime, GOM, YouTube, etc...) for your desktop computer/laptop, whatever.
I would use a button for the play/pause input. There is a button tutorial built in to the Arduino IDE (software development package) that will show you how to wire up and read one.
If you want to control your computer then use a Leonardo or Micro Arduino, because those types can be programmed to look like a keyboard to your computer.
Then send the keyboard short cut symbols to control what ever you want.
Keep in mind that every application you refer to has its own concept of what play and pause mean. There is NO universal play mechanism or pause mechanism.
I can't see ANY way to do what you want without something a lot more intelligent and capable between the Arduino and the PC, like a human.