These video show that you dont understand how autofocus works.
Contrast detection is used in samsung phone so if the contrast is low or shooting in low light then you will have slow focusing where as in high contrast it will be working fine.
After looking 1st video your contrast is too low & moreover you are taking the camera too close, you need macro mode to be used.
2nd video proves that auto focus is working fine but when you focus on indoor wall (right side) it fails to focus again due to low contrast.
So in nutshell I can say the auto focus is working fine, I had similar problems reported for i9003 phones but auto focus was not the problem. I shoot lots of view with my phone & never face problem unless I am in low contrast lighting.