CRF Error!

[killer_sai]

1.When i used x264 unrestricted 1pass constant quality HQ profile in Megui...

this is my cmds

program --profile high --level 5.1 --preset fast --thread-input --deblock -1:-1 --bframes 3 --b-adapt 2 --b-pyramid --b-bias 0 --scenecut 40 --ref 5 --rc-lookahead 40 --no-mbtree --aq-mode 1 --aq-strength 1.0 --merange 16 --me umh --subme 6 --partitions all --trellis 2 --psy-rd 1.0:0 --output "output" "input"

an error occurs in rc-lookahead!

2.i want to edit that Cmd line how Can I