The issue with encoding Sonic 3 footage—specifically for archival or high-quality web playback—comes down to two things:
If you clarify your goal (e.g., "I want to re-encode a Sonic 3 longplay to VP9" or "I found libvpx mentioned in a Sonic 3 disassembly"), I can give a precise, step-by-step answer.
– You might be looking to encode gameplay recordings, TAS (tool-assisted speedrun) videos, or fan animations of Sonic 3 using libvpx for high-efficiency web-friendly VP9 output (e.g., for YouTube, Discord, or archival). Example command: ffmpeg -i sonic3_capture.mkv -c:v libvpx-vp9 -crf 30 -b:v 0 -c:a libopus sonic3_vp9.webm