Resizing Old Video Game Footage - VirtualDub

Hi, I'm brand new to Davinci Resolve (free version). Watched a Getting Started tutorial, and liked what I saw. Most of my footage is old video game footage I record using an emulator, and then I resize it in VirtualDub. However, while trying to import footage, it seems Resolve doesn't like the codec I used (Lagarith). So I'm looking for another codec I can use in VirtualDub to compress that Resolve can work with. I've downloaded DNxHD and Cineform but they aren't working with VirtualDub (possible that I'm not installing them correctly).

It's possible that I may need to use something besides VirtualDub to resize, and I'm open to suggestions.

Your material may not be at a constant frame rate. If you're on Win 10 64bit, this GUI command line tool will do everything you need to prep files for Resolve http://hdcinematics.com/forms/V6-Download.html

Note that you'll need to install FFMPEG separately. http://hdcinematics.com/wnorton/v6-user-guide

To make things easier you can also hardware encode directly, like with the H264 Encoder from BMD,
it saves time, or you can encode H264 to another codec after that.
Take a look at the BMD products overview.
btw. you use a capture device ? if so, which one ?