Hello, this is my first post so please be easy on me. I just bought a raspberry pi 2 that had retropi preloaded on it. Ive read the instructions and looked on here and im fuzzy on a couple of things. First, I have some kinda video problem. One it loads into emulation station, my screen jumps and jerks. it continues even when you start an emulator and play a game. some times it does it the whole time you play, sometimes the screen will turn black for a sec and when it comes back on it the video is totally fine. Is there something I can do to fix this? Second, I bought this unit to play mame on and im not quite sure how to do it. I tried to load contra both contra files on it and it said missing files. so I tried to load a single rom like cadillacs and dinosausrs and it said it was invalid. im leaving them as zip files, so any help would be appreciated. This is a great site, thanks in advance for all your help!!
Hopefully they didnt charge you for retropie as well as the rpi2, cause retropie is free and quite simple to setup. (Plus its unlikely it has the latest image as that was just released today.) I’m not sure what to tell you on the video issues as I’ve never had that problem, could be an issue with your hardware or if you bought the pi secondhand it could have also had problems from the previous owner. You could try installing a new image on it (retropie 3 beta 4) and see if that works. (You’ll probably want to make a backup of your SD card first just in case)
As far as mame goes it can be a bit confusing at first to get sorted out as different emulators use different romsets even if they are the same game. You’ll likely have to rebuild your romset using a program called clrmamepro so they will be compatible with your retropie’s version of mame. See this post and accompanying video:
The retropie wiki should answer a lot of your questions if you’re just getting into retropie, it may be a bit of a learning curve at first but its worth it. I try my best to keep the wiki as updated as possible so that it is useful to newcomers especially.