[FFmpeg-user] why ffmpeg takes lot of cpu?

[comp4me]

i run this command on pc with cpu i5

ffmpeg -i rtsp://x.x.x.x -i 2.264  -preset ultrafast -filter_complex
"[0]crop=20:20:20:20[a];[a][1] overlay=0:0" http://127.0.0.1/feed.ffm
i see how much this process takes me with "top" command(ubuntu)
I see that it takes my 250% cpu 
why it takes so much cpu please?
what can i do to reduce that?




--
Sent from: http://www.ffmpeg-archive.org/