Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

I've heard that the size difference between 720p and 1080p for HEVC/h.265 is neglectable, so you should probably stick to 1080p for better quality.

But honestly I think what you want to do is neither worth the effort nor is the result very desirable.

I've been using a for loop with ffmpeg to convert to AV1

I start in the series root folder and it iterates through each seasons subfolder

for f in ./**/*.mkv; do
      ffmpeg -i "$f" -c:v libsvtav1 -crf 0 "{f%.*}.av1.mkv"; done

Since I'm happy with the quality of everything so far, I've added this to the start to make it easier to delete the old files

for f in ./**/*.mkv; do
      mv "$f" "${f%.*}.xyz.mkv"; done

And at the end I've added this to delete the old files

for f in ./**/*.xyz.mkv; do
      rm " $f"; done