Raise edge contrast to make the picture look crisp. Too much creates a white band (halo) around the edges.
After upscaling, for AI clips that came out blurry, and for previews enlarged from 480p.
AI clips often already have detail painted in, so apply only a very light amount. In ffmpeg, unsharp=5:5:0.4:5:5:0 (luma only, a little). Add film grain after sharpening (so the grain doesn't get sharpened too). Check at 100% that halos and noise don't increase on faces and sky gradients.
Add a very light luma-only sharpen to a soft AI clip: ffmpeg -i in.mp4 -vf unsharp=5:5:0.4:5:5:0 -c:a copy out.mp4. Check faces and sky gradients at 100 percent for halos, and add film grain after sharpening so the grain itself does not become harsh.
Not verified