In order to understand the quality of experience of users during watching videos, would you like to spare a few minutes to pick up several video clips. All the videos last about 12 seconds and have no audios, and you just need to give your ratings according to your subjective understanding and preference on video content, video quality, video fluency, and overall satisfaction taking on the value 1 star = bad, 2 star = poor, 3 star = fair, 4 star = good, and 5 star = excellent.