1fa6669bc0 misinterpreted the example and
changed the pixel value from 128 to 168 (thinking that it meant pixels
after scaling), but likely the original calculation was correct because
the line specifically says "of the source video". This is just confusing
not really useful information so instead change the example to a more
common resolution (1920x1080) and remove any references to the source
video resolution. Also mention video-pan-y while we're at it.
Dudemanguy
3422e5e1e8