ddragon
Your CPU is to close to "reference system 3" (4 cores Phenom @2.8 GHz) so 80% CPU load at default settings is normal. If you think it's too much just install "level 2" video profiles from start menu shortcut called "reset profiles".
Also 3.1 assumes that you're using hardware video decoder (LAV filter, for example) and I know nothing about HW decoding and .FLV format so it may be some splitter/decoder issues there.
smoothness doesn't look good
Some people think that 3.1.1 has too high threshold for scene change detection. Though I don't agree with them you still can adjust it by yourself by uncommenting "smooth.scene.limits.scene" line in overrride.js file.