The code uses elm-chan's FatFs (a small FAT32 library) to find the right sectors, and then DMAs each uncompressed video frame directly into VRAM, enabling 60FPS video playback efficiently. With the 32MiB ROM size limit no longer being an issue, I opted to not compress the videos at all, which allowed to also run other things in the game loop like GSM audio decoding, the chart-reading routines or the wireless adapter multiplayer code.

Here's the game source code: https://github.com/afska/piugba To try the video feature, you need an actual Game Boy Advance plus the EverDrive flash cart, so it's a bit niche. But I hope the video and the explanation illustrates how it works :)

Let me know what you think!