https://code.ffmpeg.org/FFmpeg/FFmpeg/issues/23049
So there's this 11 year old issue in a forgotten ffmpeg plugin and I fixed it with deepseek by putting it into a self-testing loop. Probably would have taken me a few weeks to even understand the initial code to begin with. I haven't done C work in a long ass time and have zero knowledge of even what sub pixel sampling means.
With DS4 took me a few days and a couple of dollars. And by few days I mean I checked on it a few minutes every half hour or so a few times.
I don't understand the code it wrote but it's been in production for a while now and no issues so it's good. Ended up speeding up our video processing pipeline by 20-30%.