sure! there's different ways to do it depending on what you're trying to accomplish, but the way i personally do it is like this: i edit a video to be 8-10 minutes long (any editor is fine) and save it as an 720p MP4 at the lowest bitrate that i can. i then use an online video converter to convert it to mpeg (search "MP4 to MPEG". Convertio or Veed being the best ones). i then use Meteo 1.5.0 to convert it to a .gba video file. (Meteo 1.4.0 and Meteo 1.5.0 MOD should also work. if one of those versions don't end up working for you for whatever reason, try another version). Keep the video under 32mb or it won't play. you won't know if it's 32mb or lower until it's finished converting. if it ends up being over 32mb, drop the bitrate within Meteo (you'll see the option. 120kb/s by default) until it ends up under 32mb, but try to squeeze as much bitrate in as you can for quality (although some videos still look "good" at 20kb/s)... i think that covers it. good luck! have fun!
To any other GBA Video makers who are reading this - share your experiences! I personally have never figured out how to do do more than 10 minute max, good quality videos