Finally an Open Source Capture Cartridge for the Original Game Boy!

Video game streaming has become a massive industry and top streamers bring in more viewers than many mainstream TV shows. And while many streamers display a video feed of themselves, the important action is on screen. It is easy to stream the content from a PC, but things get trickier with consoles. Modern consoles with HDMI output work with inline HDMI capture devices and there are similar devices for other video signals. But what about old handhelds that don’t have video output? To give streamers a way to capture original Game Boy content, Sebastian Staacks developed this open source GB Interceptor capture cartridge.

There are other solutions, such as emulation and special Game Boys modified for video output. But those solutions are imperfect. Emulation usually isn’t allowed in competition and many gamers (understandably) don’t want to modify original hardware. The GB Interceptor is the perfect alternative. It lets the user play on original, unmodified hardware and still get crisp video output ready for streaming. Video pipes out through a USB-C port on the side of the GB Interceptor. The gamer can plug that into their computer and it will appear like a webcam, which they can then stream to their channel.

On the technical side, the inner workings are very interesting. The GB Interceptor sits between the game cartridge and the Game Boy. But as experts already know, the Game Boy doesn’t output any video to the cartridge. The game cartridge connects to the Game Boy’s memory bus, which means the GB Interceptor only has access to that data.

This is where Staacks got really clever. Inside the GB Interceptor is a Raspberry Pi RP2040 microcontroller that is running a custom emulator that Staacks wrote. The gamer plays the actual game running on the real hardware, but the video stream comes from an emulation that exactly matches the Game Boy content. It monitors the memory bus and looks for events corresponding to in-game actions, which it then replicates in the emulation. Everything syncs up well, so viewers should see the same thing that the player sees — even though their view is of an emulation and the player’s view is the real deal.

There are, of course, a couple of small caveats. First, it doesn’t capture audio. To stream the game’s audio, the player must connect a cable to the Game Boy’s headphone jack. Second, it only works with original Game Boy games. Players can use GB Interceptor with a Game Boy Color or Game Boy Advance, but only if they’re playing original Game Boy games.

To get your hands on a GB Interceptor, you’ll either have to wait for a group buy or use the open source files to make your own. If your SMD soldering skills aren’t up to snuff, then it can be pricey to order the custom board already populated with components. In that case, you’ll probably want to wait for a group buy (check out Staacks' subreddit to try and coordinate that).